} Notifications.
		 */
		get: function( args ) {
			var collection = this, notifications, errorTypePriorities, params;
			notifications = _.values( collection._value );
			params = _.extend(
				{ sort: false },
				args
			);
			if ( params.sort ) {
				errorTypePriorities = { error: 4, warning: 3, success: 2, info: 1 };
				notifications.sort( function( a, b ) {
					var aPriority = 0, bPriority = 0;
					if ( ! _.isUndefined( errorTypePriorities[ a.type ] ) ) {
						aPriority = errorTypePriorities[ a.type ];
					}
					if ( ! _.isUndefined( errorTypePriorities[ b.type ] ) ) {
						bPriority = errorTypePriorities[ b.type ];
					}
					if ( aPriority !== bPriority ) {
						return bPriority - aPriority; // Show errors first.
					}
					return collection._addedOrder[ b.code ] - collection._addedOrder[ a.code ]; // Show newer notifications higher.
				});
			}
			return notifications;
		},
		/**
		 * Render notifications area.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		render: function() {
			var collection = this,
				notifications, hadOverlayNotification = false, hasOverlayNotification, overlayNotifications = [],
				previousNotificationsByCode = {},
				listElement, focusableElements;
			// Short-circuit if there are no container to render into.
			if ( ! collection.container || ! collection.container.length ) {
				return;
			}
			notifications = collection.get( { sort: true } );
			collection.container.toggle( 0 !== notifications.length );
			// Short-circuit if there are no changes to the notifications.
			if ( collection.container.is( collection.previousContainer ) && _.isEqual( notifications, collection.previousNotifications ) ) {
				return;
			}
			// Make sure list is part of the container.
			listElement = collection.container.children( 'ul' ).first();
			if ( ! listElement.length ) {
				listElement = $( '' );
				collection.container.append( listElement );
			}
			// Remove all notifications prior to re-rendering.
			listElement.find( '> [data-code]' ).remove();
			_.each( collection.previousNotifications, function( notification ) {
				previousNotificationsByCode[ notification.code ] = notification;
			});
			// Add all notifications in the sorted order.
			_.each( notifications, function( notification ) {
				var notificationContainer;
				if ( wp.a11y && ( ! previousNotificationsByCode[ notification.code ] || ! _.isEqual( notification.message, previousNotificationsByCode[ notification.code ].message ) ) ) {
					wp.a11y.speak( notification.message, 'assertive' );
				}
				notificationContainer = $( notification.render() );
				notification.container = notificationContainer;
				listElement.append( notificationContainer ); // @todo Consider slideDown() as enhancement.
				if ( notification.extended( api.OverlayNotification ) ) {
					overlayNotifications.push( notification );
				}
			});
			hasOverlayNotification = Boolean( overlayNotifications.length );
			if ( collection.previousNotifications ) {
				hadOverlayNotification = Boolean( _.find( collection.previousNotifications, function( notification ) {
					return notification.extended( api.OverlayNotification );
				} ) );
			}
			if ( hasOverlayNotification !== hadOverlayNotification ) {
				$( document.body ).toggleClass( 'customize-loading', hasOverlayNotification );
				collection.container.toggleClass( 'has-overlay-notifications', hasOverlayNotification );
				if ( hasOverlayNotification ) {
					collection.previousActiveElement = document.activeElement;
					$( document ).on( 'keydown', collection.constrainFocus );
				} else {
					$( document ).off( 'keydown', collection.constrainFocus );
				}
			}
			if ( hasOverlayNotification ) {
				collection.focusContainer = overlayNotifications[ overlayNotifications.length - 1 ].container;
				collection.focusContainer.prop( 'tabIndex', -1 );
				focusableElements = collection.focusContainer.find( ':focusable' );
				if ( focusableElements.length ) {
					focusableElements.first().focus();
				} else {
					collection.focusContainer.focus();
				}
			} else if ( collection.previousActiveElement ) {
				$( collection.previousActiveElement ).trigger( 'focus' );
				collection.previousActiveElement = null;
			}
			collection.previousNotifications = notifications;
			collection.previousContainer = collection.container;
			collection.trigger( 'rendered' );
		},
		/**
		 * Constrain focus on focus container.
		 *
		 * @since 4.9.0
		 *
		 * @param {jQuery.Event} event - Event.
		 * @return {void}
		 */
		constrainFocus: function constrainFocus( event ) {
			var collection = this, focusableElements;
			// Prevent keys from escaping.
			event.stopPropagation();
			if ( 9 !== event.which ) { // Tab key.
				return;
			}
			focusableElements = collection.focusContainer.find( ':focusable' );
			if ( 0 === focusableElements.length ) {
				focusableElements = collection.focusContainer;
			}
			if ( ! $.contains( collection.focusContainer[0], event.target ) || ! $.contains( collection.focusContainer[0], document.activeElement ) ) {
				event.preventDefault();
				focusableElements.first().focus();
			} else if ( focusableElements.last().is( event.target ) && ! event.shiftKey ) {
				event.preventDefault();
				focusableElements.first().focus();
			} else if ( focusableElements.first().is( event.target ) && event.shiftKey ) {
				event.preventDefault();
				focusableElements.last().focus();
			}
		}
	});
	api.Setting = api.Value.extend(/** @lends wp.customize.Setting.prototype */{
		/**
		 * Default params.
		 *
		 * @since 4.9.0
		 * @var {object}
		 */
		defaults: {
			transport: 'refresh',
			dirty: false
		},
		/**
		 * A Customizer Setting.
		 *
		 * A setting is WordPress data (theme mod, option, menu, etc.) that the user can
		 * draft changes to in the Customizer.
		 *
		 * @see PHP class WP_Customize_Setting.
		 *
		 * @constructs wp.customize.Setting
		 * @augments   wp.customize.Value
		 *
		 * @since 3.4.0
		 *
		 * @param {string}  id                          - The setting ID.
		 * @param {*}       value                       - The initial value of the setting.
		 * @param {Object}  [options={}]                - Options.
		 * @param {string}  [options.transport=refresh] - The transport to use for previewing. Supports 'refresh' and 'postMessage'.
		 * @param {boolean} [options.dirty=false]       - Whether the setting should be considered initially dirty.
		 * @param {Object}  [options.previewer]         - The Previewer instance to sync with. Defaults to wp.customize.previewer.
		 */
		initialize: function( id, value, options ) {
			var setting = this, params;
			params = _.extend(
				{ previewer: api.previewer },
				setting.defaults,
				options || {}
			);
			api.Value.prototype.initialize.call( setting, value, params );
			setting.id = id;
			setting._dirty = params.dirty; // The _dirty property is what the Customizer reads from.
			setting.notifications = new api.Notifications();
			// Whenever the setting's value changes, refresh the preview.
			setting.bind( setting.preview );
		},
		/**
		 * Refresh the preview, respective of the setting's refresh policy.
		 *
		 * If the preview hasn't sent a keep-alive message and is likely
		 * disconnected by having navigated to a non-allowed URL, then the
		 * refresh transport will be forced when postMessage is the transport.
		 * Note that postMessage does not throw an error when the recipient window
		 * fails to match the origin window, so using try/catch around the
		 * previewer.send() call to then fallback to refresh will not work.
		 *
		 * @since 3.4.0
		 * @access public
		 *
		 * @return {void}
		 */
		preview: function() {
			var setting = this, transport;
			transport = setting.transport;
			if ( 'postMessage' === transport && ! api.state( 'previewerAlive' ).get() ) {
				transport = 'refresh';
			}
			if ( 'postMessage' === transport ) {
				setting.previewer.send( 'setting', [ setting.id, setting() ] );
			} else if ( 'refresh' === transport ) {
				setting.previewer.refresh();
			}
		},
		/**
		 * Find controls associated with this setting.
		 *
		 * @since 4.6.0
		 * @return {wp.customize.Control[]} Controls associated with setting.
		 */
		findControls: function() {
			var setting = this, controls = [];
			api.control.each( function( control ) {
				_.each( control.settings, function( controlSetting ) {
					if ( controlSetting.id === setting.id ) {
						controls.push( control );
					}
				} );
			} );
			return controls;
		}
	});
	/**
	 * Current change count.
	 *
	 * @alias wp.customize._latestRevision
	 *
	 * @since 4.7.0
	 * @type {number}
	 * @protected
	 */
	api._latestRevision = 0;
	/**
	 * Last revision that was saved.
	 *
	 * @alias wp.customize._lastSavedRevision
	 *
	 * @since 4.7.0
	 * @type {number}
	 * @protected
	 */
	api._lastSavedRevision = 0;
	/**
	 * Latest revisions associated with the updated setting.
	 *
	 * @alias wp.customize._latestSettingRevisions
	 *
	 * @since 4.7.0
	 * @type {object}
	 * @protected
	 */
	api._latestSettingRevisions = {};
	/*
	 * Keep track of the revision associated with each updated setting so that
	 * requestChangesetUpdate knows which dirty settings to include. Also, once
	 * ready is triggered and all initial settings have been added, increment
	 * revision for each newly-created initially-dirty setting so that it will
	 * also be included in changeset update requests.
	 */
	api.bind( 'change', function incrementChangedSettingRevision( setting ) {
		api._latestRevision += 1;
		api._latestSettingRevisions[ setting.id ] = api._latestRevision;
	} );
	api.bind( 'ready', function() {
		api.bind( 'add', function incrementCreatedSettingRevision( setting ) {
			if ( setting._dirty ) {
				api._latestRevision += 1;
				api._latestSettingRevisions[ setting.id ] = api._latestRevision;
			}
		} );
	} );
	/**
	 * Get the dirty setting values.
	 *
	 * @alias wp.customize.dirtyValues
	 *
	 * @since 4.7.0
	 * @access public
	 *
	 * @param {Object} [options] Options.
	 * @param {boolean} [options.unsaved=false] Whether only values not saved yet into a changeset will be returned (differential changes).
	 * @return {Object} Dirty setting values.
	 */
	api.dirtyValues = function dirtyValues( options ) {
		var values = {};
		api.each( function( setting ) {
			var settingRevision;
			if ( ! setting._dirty ) {
				return;
			}
			settingRevision = api._latestSettingRevisions[ setting.id ];
			// Skip including settings that have already been included in the changeset, if only requesting unsaved.
			if ( api.state( 'changesetStatus' ).get() && ( options && options.unsaved ) && ( _.isUndefined( settingRevision ) || settingRevision <= api._lastSavedRevision ) ) {
				return;
			}
			values[ setting.id ] = setting.get();
		} );
		return values;
	};
	/**
	 * Request updates to the changeset.
	 *
	 * @alias wp.customize.requestChangesetUpdate
	 *
	 * @since 4.7.0
	 * @access public
	 *
	 * @param {Object}  [changes] - Mapping of setting IDs to setting params each normally including a value property, or mapping to null.
	 *                             If not provided, then the changes will still be obtained from unsaved dirty settings.
	 * @param {Object}  [args] - Additional options for the save request.
	 * @param {boolean} [args.autosave=false] - Whether changes will be stored in autosave revision if the changeset has been promoted from an auto-draft.
	 * @param {boolean} [args.force=false] - Send request to update even when there are no changes to submit. This can be used to request the latest status of the changeset on the server.
	 * @param {string}  [args.title] - Title to update in the changeset. Optional.
	 * @param {string}  [args.date] - Date to update in the changeset. Optional.
	 * @return {jQuery.Promise} Promise resolving with the response data.
	 */
	api.requestChangesetUpdate = function requestChangesetUpdate( changes, args ) {
		var deferred, request, submittedChanges = {}, data, submittedArgs;
		deferred = new $.Deferred();
		// Prevent attempting changeset update while request is being made.
		if ( 0 !== api.state( 'processing' ).get() ) {
			deferred.reject( 'already_processing' );
			return deferred.promise();
		}
		submittedArgs = _.extend( {
			title: null,
			date: null,
			autosave: false,
			force: false
		}, args );
		if ( changes ) {
			_.extend( submittedChanges, changes );
		}
		// Ensure all revised settings (changes pending save) are also included, but not if marked for deletion in changes.
		_.each( api.dirtyValues( { unsaved: true } ), function( dirtyValue, settingId ) {
			if ( ! changes || null !== changes[ settingId ] ) {
				submittedChanges[ settingId ] = _.extend(
					{},
					submittedChanges[ settingId ] || {},
					{ value: dirtyValue }
				);
			}
		} );
		// Allow plugins to attach additional params to the settings.
		api.trigger( 'changeset-save', submittedChanges, submittedArgs );
		// Short-circuit when there are no pending changes.
		if ( ! submittedArgs.force && _.isEmpty( submittedChanges ) && null === submittedArgs.title && null === submittedArgs.date ) {
			deferred.resolve( {} );
			return deferred.promise();
		}
		// A status would cause a revision to be made, and for this wp.customize.previewer.save() should be used.
		// Status is also disallowed for revisions regardless.
		if ( submittedArgs.status ) {
			return deferred.reject( { code: 'illegal_status_in_changeset_update' } ).promise();
		}
		// Dates not beung allowed for revisions are is a technical limitation of post revisions.
		if ( submittedArgs.date && submittedArgs.autosave ) {
			return deferred.reject( { code: 'illegal_autosave_with_date_gmt' } ).promise();
		}
		// Make sure that publishing a changeset waits for all changeset update requests to complete.
		api.state( 'processing' ).set( api.state( 'processing' ).get() + 1 );
		deferred.always( function() {
			api.state( 'processing' ).set( api.state( 'processing' ).get() - 1 );
		} );
		// Ensure that if any plugins add data to save requests by extending query() that they get included here.
		data = api.previewer.query( { excludeCustomizedSaved: true } );
		delete data.customized; // Being sent in customize_changeset_data instead.
		_.extend( data, {
			nonce: api.settings.nonce.save,
			customize_theme: api.settings.theme.stylesheet,
			customize_changeset_data: JSON.stringify( submittedChanges )
		} );
		if ( null !== submittedArgs.title ) {
			data.customize_changeset_title = submittedArgs.title;
		}
		if ( null !== submittedArgs.date ) {
			data.customize_changeset_date = submittedArgs.date;
		}
		if ( false !== submittedArgs.autosave ) {
			data.customize_changeset_autosave = 'true';
		}
		// Allow plugins to modify the params included with the save request.
		api.trigger( 'save-request-params', data );
		request = wp.ajax.post( 'customize_save', data );
		request.done( function requestChangesetUpdateDone( data ) {
			var savedChangesetValues = {};
			// Ensure that all settings updated subsequently will be included in the next changeset update request.
			api._lastSavedRevision = Math.max( api._latestRevision, api._lastSavedRevision );
			api.state( 'changesetStatus' ).set( data.changeset_status );
			if ( data.changeset_date ) {
				api.state( 'changesetDate' ).set( data.changeset_date );
			}
			deferred.resolve( data );
			api.trigger( 'changeset-saved', data );
			if ( data.setting_validities ) {
				_.each( data.setting_validities, function( validity, settingId ) {
					if ( true === validity && _.isObject( submittedChanges[ settingId ] ) && ! _.isUndefined( submittedChanges[ settingId ].value ) ) {
						savedChangesetValues[ settingId ] = submittedChanges[ settingId ].value;
					}
				} );
			}
			api.previewer.send( 'changeset-saved', _.extend( {}, data, { saved_changeset_values: savedChangesetValues } ) );
		} );
		request.fail( function requestChangesetUpdateFail( data ) {
			deferred.reject( data );
			api.trigger( 'changeset-error', data );
		} );
		request.always( function( data ) {
			if ( data.setting_validities ) {
				api._handleSettingValidities( {
					settingValidities: data.setting_validities
				} );
			}
		} );
		return deferred.promise();
	};
	/**
	 * Watch all changes to Value properties, and bubble changes to parent Values instance
	 *
	 * @alias wp.customize.utils.bubbleChildValueChanges
	 *
	 * @since 4.1.0
	 *
	 * @param {wp.customize.Class} instance
	 * @param {Array}              properties  The names of the Value instances to watch.
	 */
	api.utils.bubbleChildValueChanges = function ( instance, properties ) {
		$.each( properties, function ( i, key ) {
			instance[ key ].bind( function ( to, from ) {
				if ( instance.parent && to !== from ) {
					instance.parent.trigger( 'change', instance );
				}
			} );
		} );
	};
	/**
	 * Expand a panel, section, or control and focus on the first focusable element.
	 *
	 * @alias wp.customize~focus
	 *
	 * @since 4.1.0
	 *
	 * @param {Object}   [params]
	 * @param {Function} [params.completeCallback]
	 */
	focus = function ( params ) {
		var construct, completeCallback, focus, focusElement, sections;
		construct = this;
		params = params || {};
		focus = function () {
			// If a child section is currently expanded, collapse it.
			if ( construct.extended( api.Panel ) ) {
				sections = construct.sections();
				if ( 1 < sections.length ) {
					sections.forEach( function ( section ) {
						if ( section.expanded() ) {
							section.collapse();
						}
					} );
				}
			}
			var focusContainer;
			if ( ( construct.extended( api.Panel ) || construct.extended( api.Section ) ) && construct.expanded && construct.expanded() ) {
				focusContainer = construct.contentContainer;
			} else {
				focusContainer = construct.container;
			}
			focusElement = focusContainer.find( '.control-focus:first' );
			if ( 0 === focusElement.length ) {
				// Note that we can't use :focusable due to a jQuery UI issue. See: https://github.com/jquery/jquery-ui/pull/1583
				focusElement = focusContainer.find( 'input, select, textarea, button, object, a[href], [tabindex]' ).filter( ':visible' ).first();
			}
			focusElement.focus();
		};
		if ( params.completeCallback ) {
			completeCallback = params.completeCallback;
			params.completeCallback = function () {
				focus();
				completeCallback();
			};
		} else {
			params.completeCallback = focus;
		}
		api.state( 'paneVisible' ).set( true );
		if ( construct.expand ) {
			construct.expand( params );
		} else {
			params.completeCallback();
		}
	};
	/**
	 * Stable sort for Panels, Sections, and Controls.
	 *
	 * If a.priority() === b.priority(), then sort by their respective params.instanceNumber.
	 *
	 * @alias wp.customize.utils.prioritySort
	 *
	 * @since 4.1.0
	 *
	 * @param {(wp.customize.Panel|wp.customize.Section|wp.customize.Control)} a
	 * @param {(wp.customize.Panel|wp.customize.Section|wp.customize.Control)} b
	 * @return {number}
	 */
	api.utils.prioritySort = function ( a, b ) {
		if ( a.priority() === b.priority() && typeof a.params.instanceNumber === 'number' && typeof b.params.instanceNumber === 'number' ) {
			return a.params.instanceNumber - b.params.instanceNumber;
		} else {
			return a.priority() - b.priority();
		}
	};
	/**
	 * Return whether the supplied Event object is for a keydown event but not the Enter key.
	 *
	 * @alias wp.customize.utils.isKeydownButNotEnterEvent
	 *
	 * @since 4.1.0
	 *
	 * @param {jQuery.Event} event
	 * @return {boolean}
	 */
	api.utils.isKeydownButNotEnterEvent = function ( event ) {
		return ( 'keydown' === event.type && 13 !== event.which );
	};
	/**
	 * Return whether the two lists of elements are the same and are in the same order.
	 *
	 * @alias wp.customize.utils.areElementListsEqual
	 *
	 * @since 4.1.0
	 *
	 * @param {Array|jQuery} listA
	 * @param {Array|jQuery} listB
	 * @return {boolean}
	 */
	api.utils.areElementListsEqual = function ( listA, listB ) {
		var equal = (
			listA.length === listB.length && // If lists are different lengths, then naturally they are not equal.
			-1 === _.indexOf( _.map(         // Are there any false values in the list returned by map?
				_.zip( listA, listB ),       // Pair up each element between the two lists.
				function ( pair ) {
					return $( pair[0] ).is( pair[1] ); // Compare to see if each pair is equal.
				}
			), false ) // Check for presence of false in map's return value.
		);
		return equal;
	};
	/**
	 * Highlight the existence of a button.
	 *
	 * This function reminds the user of a button represented by the specified
	 * UI element, after an optional delay. If the user focuses the element
	 * before the delay passes, the reminder is canceled.
	 *
	 * @alias wp.customize.utils.highlightButton
	 *
	 * @since 4.9.0
	 *
	 * @param {jQuery} button - The element to highlight.
	 * @param {Object} [options] - Options.
	 * @param {number} [options.delay=0] - Delay in milliseconds.
	 * @param {jQuery} [options.focusTarget] - A target for user focus that defaults to the highlighted element.
	 *                                         If the user focuses the target before the delay passes, the reminder
	 *                                         is canceled. This option exists to accommodate compound buttons
	 *                                         containing auxiliary UI, such as the Publish button augmented with a
	 *                                         Settings button.
	 * @return {Function} An idempotent function that cancels the reminder.
	 */
	api.utils.highlightButton = function highlightButton( button, options ) {
		var animationClass = 'button-see-me',
			canceled = false,
			params;
		params = _.extend(
			{
				delay: 0,
				focusTarget: button
			},
			options
		);
		function cancelReminder() {
			canceled = true;
		}
		params.focusTarget.on( 'focusin', cancelReminder );
		setTimeout( function() {
			params.focusTarget.off( 'focusin', cancelReminder );
			if ( ! canceled ) {
				button.addClass( animationClass );
				button.one( 'animationend', function() {
					/*
					 * Remove animation class to avoid situations in Customizer where
					 * DOM nodes are moved (re-inserted) and the animation repeats.
					 */
					button.removeClass( animationClass );
				} );
			}
		}, params.delay );
		return cancelReminder;
	};
	/**
	 * Get current timestamp adjusted for server clock time.
	 *
	 * Same functionality as the `current_time( 'mysql', false )` function in PHP.
	 *
	 * @alias wp.customize.utils.getCurrentTimestamp
	 *
	 * @since 4.9.0
	 *
	 * @return {number} Current timestamp.
	 */
	api.utils.getCurrentTimestamp = function getCurrentTimestamp() {
		var currentDate, currentClientTimestamp, timestampDifferential;
		currentClientTimestamp = _.now();
		currentDate = new Date( api.settings.initialServerDate.replace( /-/g, '/' ) );
		timestampDifferential = currentClientTimestamp - api.settings.initialClientTimestamp;
		timestampDifferential += api.settings.initialClientTimestamp - api.settings.initialServerTimestamp;
		currentDate.setTime( currentDate.getTime() + timestampDifferential );
		return currentDate.getTime();
	};
	/**
	 * Get remaining time of when the date is set.
	 *
	 * @alias wp.customize.utils.getRemainingTime
	 *
	 * @since 4.9.0
	 *
	 * @param {string|number|Date} datetime - Date time or timestamp of the future date.
	 * @return {number} remainingTime - Remaining time in milliseconds.
	 */
	api.utils.getRemainingTime = function getRemainingTime( datetime ) {
		var millisecondsDivider = 1000, remainingTime, timestamp;
		if ( datetime instanceof Date ) {
			timestamp = datetime.getTime();
		} else if ( 'string' === typeof datetime ) {
			timestamp = ( new Date( datetime.replace( /-/g, '/' ) ) ).getTime();
		} else {
			timestamp = datetime;
		}
		remainingTime = timestamp - api.utils.getCurrentTimestamp();
		remainingTime = Math.ceil( remainingTime / millisecondsDivider );
		return remainingTime;
	};
	/**
	 * Return browser supported `transitionend` event name.
	 *
	 * @since 4.7.0
	 *
	 * @ignore
	 *
	 * @return {string|null} Normalized `transitionend` event name or null if CSS transitions are not supported.
	 */
	normalizedTransitionendEventName = (function () {
		var el, transitions, prop;
		el = document.createElement( 'div' );
		transitions = {
			'transition'      : 'transitionend',
			'OTransition'     : 'oTransitionEnd',
			'MozTransition'   : 'transitionend',
			'WebkitTransition': 'webkitTransitionEnd'
		};
		prop = _.find( _.keys( transitions ), function( prop ) {
			return ! _.isUndefined( el.style[ prop ] );
		} );
		if ( prop ) {
			return transitions[ prop ];
		} else {
			return null;
		}
	})();
	Container = api.Class.extend(/** @lends wp.customize~Container.prototype */{
		defaultActiveArguments: { duration: 'fast', completeCallback: $.noop },
		defaultExpandedArguments: { duration: 'fast', completeCallback: $.noop },
		containerType: 'container',
		defaults: {
			title: '',
			description: '',
			priority: 100,
			type: 'default',
			content: null,
			active: true,
			instanceNumber: null
		},
		/**
		 * Base class for Panel and Section.
		 *
		 * @constructs wp.customize~Container
		 * @augments   wp.customize.Class
		 *
		 * @since 4.1.0
		 *
		 * @borrows wp.customize~focus as focus
		 *
		 * @param {string}  id - The ID for the container.
		 * @param {Object}  options - Object containing one property: params.
		 * @param {string}  options.title - Title shown when panel is collapsed and expanded.
		 * @param {string}  [options.description] - Description shown at the top of the panel.
		 * @param {number}  [options.priority=100] - The sort priority for the panel.
		 * @param {string}  [options.templateId] - Template selector for container.
		 * @param {string}  [options.type=default] - The type of the panel. See wp.customize.panelConstructor.
		 * @param {string}  [options.content] - The markup to be used for the panel container. If empty, a JS template is used.
		 * @param {boolean} [options.active=true] - Whether the panel is active or not.
		 * @param {Object}  [options.params] - Deprecated wrapper for the above properties.
		 */
		initialize: function ( id, options ) {
			var container = this;
			container.id = id;
			if ( ! Container.instanceCounter ) {
				Container.instanceCounter = 0;
			}
			Container.instanceCounter++;
			$.extend( container, {
				params: _.defaults(
					options.params || options, // Passing the params is deprecated.
					container.defaults
				)
			} );
			if ( ! container.params.instanceNumber ) {
				container.params.instanceNumber = Container.instanceCounter;
			}
			container.notifications = new api.Notifications();
			container.templateSelector = container.params.templateId || 'customize-' + container.containerType + '-' + container.params.type;
			container.container = $( container.params.content );
			if ( 0 === container.container.length ) {
				container.container = $( container.getContainer() );
			}
			container.headContainer = container.container;
			container.contentContainer = container.getContent();
			container.container = container.container.add( container.contentContainer );
			container.deferred = {
				embedded: new $.Deferred()
			};
			container.priority = new api.Value();
			container.active = new api.Value();
			container.activeArgumentsQueue = [];
			container.expanded = new api.Value();
			container.expandedArgumentsQueue = [];
			container.active.bind( function ( active ) {
				var args = container.activeArgumentsQueue.shift();
				args = $.extend( {}, container.defaultActiveArguments, args );
				active = ( active && container.isContextuallyActive() );
				container.onChangeActive( active, args );
			});
			container.expanded.bind( function ( expanded ) {
				var args = container.expandedArgumentsQueue.shift();
				args = $.extend( {}, container.defaultExpandedArguments, args );
				container.onChangeExpanded( expanded, args );
			});
			container.deferred.embedded.done( function () {
				container.setupNotifications();
				container.attachEvents();
			});
			api.utils.bubbleChildValueChanges( container, [ 'priority', 'active' ] );
			container.priority.set( container.params.priority );
			container.active.set( container.params.active );
			container.expanded.set( false );
		},
		/**
		 * Get the element that will contain the notifications.
		 *
		 * @since 4.9.0
		 * @return {jQuery} Notification container element.
		 */
		getNotificationsContainerElement: function() {
			var container = this;
			return container.contentContainer.find( '.customize-control-notifications-container:first' );
		},
		/**
		 * Set up notifications.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		setupNotifications: function() {
			var container = this, renderNotifications;
			container.notifications.container = container.getNotificationsContainerElement();
			// Render notifications when they change and when the construct is expanded.
			renderNotifications = function() {
				if ( container.expanded.get() ) {
					container.notifications.render();
				}
			};
			container.expanded.bind( renderNotifications );
			renderNotifications();
			container.notifications.bind( 'change', _.debounce( renderNotifications ) );
		},
		/**
		 * @since 4.1.0
		 *
		 * @abstract
		 */
		ready: function() {},
		/**
		 * Get the child models associated with this parent, sorting them by their priority Value.
		 *
		 * @since 4.1.0
		 *
		 * @param {string} parentType
		 * @param {string} childType
		 * @return {Array}
		 */
		_children: function ( parentType, childType ) {
			var parent = this,
				children = [];
			api[ childType ].each( function ( child ) {
				if ( child[ parentType ].get() === parent.id ) {
					children.push( child );
				}
			} );
			children.sort( api.utils.prioritySort );
			return children;
		},
		/**
		 * To override by subclass, to return whether the container has active children.
		 *
		 * @since 4.1.0
		 *
		 * @abstract
		 */
		isContextuallyActive: function () {
			throw new Error( 'Container.isContextuallyActive() must be overridden in a subclass.' );
		},
		/**
		 * Active state change handler.
		 *
		 * Shows the container if it is active, hides it if not.
		 *
		 * To override by subclass, update the container's UI to reflect the provided active state.
		 *
		 * @since 4.1.0
		 *
		 * @param {boolean}  active - The active state to transiution to.
		 * @param {Object}   [args] - Args.
		 * @param {Object}   [args.duration] - The duration for the slideUp/slideDown animation.
		 * @param {boolean}  [args.unchanged] - Whether the state is already known to not be changed, and so short-circuit with calling completeCallback early.
		 * @param {Function} [args.completeCallback] - Function to call when the slideUp/slideDown has completed.
		 */
		onChangeActive: function( active, args ) {
			var construct = this,
				headContainer = construct.headContainer,
				duration, expandedOtherPanel;
			if ( args.unchanged ) {
				if ( args.completeCallback ) {
					args.completeCallback();
				}
				return;
			}
			duration = ( 'resolved' === api.previewer.deferred.active.state() ? args.duration : 0 );
			if ( construct.extended( api.Panel ) ) {
				// If this is a panel is not currently expanded but another panel is expanded, do not animate.
				api.panel.each(function ( panel ) {
					if ( panel !== construct && panel.expanded() ) {
						expandedOtherPanel = panel;
						duration = 0;
					}
				});
				// Collapse any expanded sections inside of this panel first before deactivating.
				if ( ! active ) {
					_.each( construct.sections(), function( section ) {
						section.collapse( { duration: 0 } );
					} );
				}
			}
			if ( ! $.contains( document, headContainer.get( 0 ) ) ) {
				// If the element is not in the DOM, then jQuery.fn.slideUp() does nothing.
				// In this case, a hard toggle is required instead.
				headContainer.toggle( active );
				if ( args.completeCallback ) {
					args.completeCallback();
				}
			} else if ( active ) {
				headContainer.slideDown( duration, args.completeCallback );
			} else {
				if ( construct.expanded() ) {
					construct.collapse({
						duration: duration,
						completeCallback: function() {
							headContainer.slideUp( duration, args.completeCallback );
						}
					});
				} else {
					headContainer.slideUp( duration, args.completeCallback );
				}
			}
		},
		/**
		 * @since 4.1.0
		 *
		 * @param {boolean} active
		 * @param {Object}  [params]
		 * @return {boolean} False if state already applied.
		 */
		_toggleActive: function ( active, params ) {
			var self = this;
			params = params || {};
			if ( ( active && this.active.get() ) || ( ! active && ! this.active.get() ) ) {
				params.unchanged = true;
				self.onChangeActive( self.active.get(), params );
				return false;
			} else {
				params.unchanged = false;
				this.activeArgumentsQueue.push( params );
				this.active.set( active );
				return true;
			}
		},
		/**
		 * @param {Object} [params]
		 * @return {boolean} False if already active.
		 */
		activate: function ( params ) {
			return this._toggleActive( true, params );
		},
		/**
		 * @param {Object} [params]
		 * @return {boolean} False if already inactive.
		 */
		deactivate: function ( params ) {
			return this._toggleActive( false, params );
		},
		/**
		 * To override by subclass, update the container's UI to reflect the provided active state.
		 * @abstract
		 */
		onChangeExpanded: function () {
			throw new Error( 'Must override with subclass.' );
		},
		/**
		 * Handle the toggle logic for expand/collapse.
		 *
		 * @param {boolean}  expanded - The new state to apply.
		 * @param {Object}   [params] - Object containing options for expand/collapse.
		 * @param {Function} [params.completeCallback] - Function to call when expansion/collapse is complete.
		 * @return {boolean} False if state already applied or active state is false.
		 */
		_toggleExpanded: function( expanded, params ) {
			var instance = this, previousCompleteCallback;
			params = params || {};
			previousCompleteCallback = params.completeCallback;
			// Short-circuit expand() if the instance is not active.
			if ( expanded && ! instance.active() ) {
				return false;
			}
			api.state( 'paneVisible' ).set( true );
			params.completeCallback = function() {
				if ( previousCompleteCallback ) {
					previousCompleteCallback.apply( instance, arguments );
				}
				if ( expanded ) {
					instance.container.trigger( 'expanded' );
				} else {
					instance.container.trigger( 'collapsed' );
				}
			};
			if ( ( expanded && instance.expanded.get() ) || ( ! expanded && ! instance.expanded.get() ) ) {
				params.unchanged = true;
				instance.onChangeExpanded( instance.expanded.get(), params );
				return false;
			} else {
				params.unchanged = false;
				instance.expandedArgumentsQueue.push( params );
				instance.expanded.set( expanded );
				return true;
			}
		},
		/**
		 * @param {Object} [params]
		 * @return {boolean} False if already expanded or if inactive.
		 */
		expand: function ( params ) {
			return this._toggleExpanded( true, params );
		},
		/**
		 * @param {Object} [params]
		 * @return {boolean} False if already collapsed.
		 */
		collapse: function ( params ) {
			return this._toggleExpanded( false, params );
		},
		/**
		 * Animate container state change if transitions are supported by the browser.
		 *
		 * @since 4.7.0
		 * @private
		 *
		 * @param {function} completeCallback Function to be called after transition is completed.
		 * @return {void}
		 */
		_animateChangeExpanded: function( completeCallback ) {
			// Return if CSS transitions are not supported or if reduced motion is enabled.
			if ( ! normalizedTransitionendEventName || isReducedMotion ) {
				// Schedule the callback until the next tick to prevent focus loss.
				_.defer( function () {
					if ( completeCallback ) {
						completeCallback();
					}
				} );
				return;
			}
			var construct = this,
				content = construct.contentContainer,
				overlay = content.closest( '.wp-full-overlay' ),
				elements, transitionEndCallback, transitionParentPane;
			// Determine set of elements that are affected by the animation.
			elements = overlay.add( content );
			if ( ! construct.panel || '' === construct.panel() ) {
				transitionParentPane = true;
			} else if ( api.panel( construct.panel() ).contentContainer.hasClass( 'skip-transition' ) ) {
				transitionParentPane = true;
			} else {
				transitionParentPane = false;
			}
			if ( transitionParentPane ) {
				elements = elements.add( '#customize-info, .customize-pane-parent' );
			}
			// Handle `transitionEnd` event.
			transitionEndCallback = function( e ) {
				if ( 2 !== e.eventPhase || ! $( e.target ).is( content ) ) {
					return;
				}
				content.off( normalizedTransitionendEventName, transitionEndCallback );
				elements.removeClass( 'busy' );
				if ( completeCallback ) {
					completeCallback();
				}
			};
			content.on( normalizedTransitionendEventName, transitionEndCallback );
			elements.addClass( 'busy' );
			// Prevent screen flicker when pane has been scrolled before expanding.
			_.defer( function() {
				var container = content.closest( '.wp-full-overlay-sidebar-content' ),
					currentScrollTop = container.scrollTop(),
					previousScrollTop = content.data( 'previous-scrollTop' ) || 0,
					expanded = construct.expanded();
				if ( expanded && 0 < currentScrollTop ) {
					content.css( 'top', currentScrollTop + 'px' );
					content.data( 'previous-scrollTop', currentScrollTop );
				} else if ( ! expanded && 0 < currentScrollTop + previousScrollTop ) {
					content.css( 'top', previousScrollTop - currentScrollTop + 'px' );
					container.scrollTop( previousScrollTop );
				}
			} );
		},
		/*
		 * is documented using @borrows in the constructor.
		 */
		focus: focus,
		/**
		 * Return the container html, generated from its JS template, if it exists.
		 *
		 * @since 4.3.0
		 */
		getContainer: function () {
			var template,
				container = this;
			if ( 0 !== $( '#tmpl-' + container.templateSelector ).length ) {
				template = wp.template( container.templateSelector );
			} else {
				template = wp.template( 'customize-' + container.containerType + '-default' );
			}
			if ( template && container.container ) {
				return template( _.extend(
					{ id: container.id },
					container.params
				) ).toString().trim();
			}
			return '';
		},
		/**
		 * Find content element which is displayed when the section is expanded.
		 *
		 * After a construct is initialized, the return value will be available via the `contentContainer` property.
		 * By default the element will be related it to the parent container with `aria-owns` and detached.
		 * Custom panels and sections (such as the `NewMenuSection`) that do not have a sliding pane should
		 * just return the content element without needing to add the `aria-owns` element or detach it from
		 * the container. Such non-sliding pane custom sections also need to override the `onChangeExpanded`
		 * method to handle animating the panel/section into and out of view.
		 *
		 * @since 4.7.0
		 * @access public
		 *
		 * @return {jQuery} Detached content element.
		 */
		getContent: function() {
			var construct = this,
				container = construct.container,
				content = container.find( '.accordion-section-content, .control-panel-content' ).first(),
				contentId = 'sub-' + container.attr( 'id' ),
				ownedElements = contentId,
				alreadyOwnedElements = container.attr( 'aria-owns' );
			if ( alreadyOwnedElements ) {
				ownedElements = ownedElements + ' ' + alreadyOwnedElements;
			}
			container.attr( 'aria-owns', ownedElements );
			return content.detach().attr( {
				'id': contentId,
				'class': 'customize-pane-child ' + content.attr( 'class' ) + ' ' + container.attr( 'class' )
			} );
		}
	});
	api.Section = Container.extend(/** @lends wp.customize.Section.prototype */{
		containerType: 'section',
		containerParent: '#customize-theme-controls',
		containerPaneParent: '.customize-pane-parent',
		defaults: {
			title: '',
			description: '',
			priority: 100,
			type: 'default',
			content: null,
			active: true,
			instanceNumber: null,
			panel: null,
			customizeAction: ''
		},
		/**
		 * @constructs wp.customize.Section
		 * @augments   wp.customize~Container
		 *
		 * @since 4.1.0
		 *
		 * @param {string}  id - The ID for the section.
		 * @param {Object}  options - Options.
		 * @param {string}  options.title - Title shown when section is collapsed and expanded.
		 * @param {string}  [options.description] - Description shown at the top of the section.
		 * @param {number}  [options.priority=100] - The sort priority for the section.
		 * @param {string}  [options.type=default] - The type of the section. See wp.customize.sectionConstructor.
		 * @param {string}  [options.content] - The markup to be used for the section container. If empty, a JS template is used.
		 * @param {boolean} [options.active=true] - Whether the section is active or not.
		 * @param {string}  options.panel - The ID for the panel this section is associated with.
		 * @param {string}  [options.customizeAction] - Additional context information shown before the section title when expanded.
		 * @param {Object}  [options.params] - Deprecated wrapper for the above properties.
		 */
		initialize: function ( id, options ) {
			var section = this, params;
			params = options.params || options;
			// Look up the type if one was not supplied.
			if ( ! params.type ) {
				_.find( api.sectionConstructor, function( Constructor, type ) {
					if ( Constructor === section.constructor ) {
						params.type = type;
						return true;
					}
					return false;
				} );
			}
			Container.prototype.initialize.call( section, id, params );
			section.id = id;
			section.panel = new api.Value();
			section.panel.bind( function ( id ) {
				$( section.headContainer ).toggleClass( 'control-subsection', !! id );
			});
			section.panel.set( section.params.panel || '' );
			api.utils.bubbleChildValueChanges( section, [ 'panel' ] );
			section.embed();
			section.deferred.embedded.done( function () {
				section.ready();
			});
		},
		/**
		 * Embed the container in the DOM when any parent panel is ready.
		 *
		 * @since 4.1.0
		 */
		embed: function () {
			var inject,
				section = this;
			section.containerParent = api.ensure( section.containerParent );
			// Watch for changes to the panel state.
			inject = function ( panelId ) {
				var parentContainer;
				if ( panelId ) {
					// The panel has been supplied, so wait until the panel object is registered.
					api.panel( panelId, function ( panel ) {
						// The panel has been registered, wait for it to become ready/initialized.
						panel.deferred.embedded.done( function () {
							parentContainer = panel.contentContainer;
							if ( ! section.headContainer.parent().is( parentContainer ) ) {
								parentContainer.append( section.headContainer );
							}
							if ( ! section.contentContainer.parent().is( section.headContainer ) ) {
								section.containerParent.append( section.contentContainer );
							}
							section.deferred.embedded.resolve();
						});
					} );
				} else {
					// There is no panel, so embed the section in the root of the customizer.
					parentContainer = api.ensure( section.containerPaneParent );
					if ( ! section.headContainer.parent().is( parentContainer ) ) {
						parentContainer.append( section.headContainer );
					}
					if ( ! section.contentContainer.parent().is( section.headContainer ) ) {
						section.containerParent.append( section.contentContainer );
					}
					section.deferred.embedded.resolve();
				}
			};
			section.panel.bind( inject );
			inject( section.panel.get() ); // Since a section may never get a panel, assume that it won't ever get one.
		},
		/**
		 * Add behaviors for the accordion section.
		 *
		 * @since 4.1.0
		 */
		attachEvents: function () {
			var meta, content, section = this;
			if ( section.container.hasClass( 'cannot-expand' ) ) {
				return;
			}
			// Expand/Collapse accordion sections on click.
			section.container.find( '.accordion-section-title button, .customize-section-back, .accordion-section-title[tabindex]' ).on( 'click keydown', function( event ) {
				if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
					return;
				}
				event.preventDefault(); // Keep this AFTER the key filter above.
				if ( section.expanded() ) {
					section.collapse();
				} else {
					section.expand();
				}
			});
			// This is very similar to what is found for api.Panel.attachEvents().
			section.container.find( '.customize-section-title .customize-help-toggle' ).on( 'click', function() {
				meta = section.container.find( '.section-meta' );
				if ( meta.hasClass( 'cannot-expand' ) ) {
					return;
				}
				content = meta.find( '.customize-section-description:first' );
				content.toggleClass( 'open' );
				content.slideToggle( section.defaultExpandedArguments.duration, function() {
					content.trigger( 'toggled' );
				} );
				$( this ).attr( 'aria-expanded', function( i, attr ) {
					return 'true' === attr ? 'false' : 'true';
				});
			});
		},
		/**
		 * Return whether this section has any active controls.
		 *
		 * @since 4.1.0
		 *
		 * @return {boolean}
		 */
		isContextuallyActive: function () {
			var section = this,
				controls = section.controls(),
				activeCount = 0;
			_( controls ).each( function ( control ) {
				if ( control.active() ) {
					activeCount += 1;
				}
			} );
			return ( activeCount !== 0 );
		},
		/**
		 * Get the controls that are associated with this section, sorted by their priority Value.
		 *
		 * @since 4.1.0
		 *
		 * @return {Array}
		 */
		controls: function () {
			return this._children( 'section', 'control' );
		},
		/**
		 * Update UI to reflect expanded state.
		 *
		 * @since 4.1.0
		 *
		 * @param {boolean} expanded
		 * @param {Object}  args
		 */
		onChangeExpanded: function ( expanded, args ) {
			var section = this,
				container = section.headContainer.closest( '.wp-full-overlay-sidebar-content' ),
				content = section.contentContainer,
				overlay = section.headContainer.closest( '.wp-full-overlay' ),
				backBtn = content.find( '.customize-section-back' ),
				sectionTitle = section.headContainer.find( '.accordion-section-title button, .accordion-section-title[tabindex]' ).first(),
				expand, panel;
			if ( expanded && ! content.hasClass( 'open' ) ) {
				if ( args.unchanged ) {
					expand = args.completeCallback;
				} else {
					expand = function() {
						section._animateChangeExpanded( function() {
							backBtn.trigger( 'focus' );
							content.css( 'top', '' );
							container.scrollTop( 0 );
							if ( args.completeCallback ) {
								args.completeCallback();
							}
						} );
						content.addClass( 'open' );
						overlay.addClass( 'section-open' );
						api.state( 'expandedSection' ).set( section );
					}.bind( this );
				}
				if ( ! args.allowMultiple ) {
					api.section.each( function ( otherSection ) {
						if ( otherSection !== section ) {
							otherSection.collapse( { duration: args.duration } );
						}
					});
				}
				if ( section.panel() ) {
					api.panel( section.panel() ).expand({
						duration: args.duration,
						completeCallback: expand
					});
				} else {
					if ( ! args.allowMultiple ) {
						api.panel.each( function( panel ) {
							panel.collapse();
						});
					}
					expand();
				}
			} else if ( ! expanded && content.hasClass( 'open' ) ) {
				if ( section.panel() ) {
					panel = api.panel( section.panel() );
					if ( panel.contentContainer.hasClass( 'skip-transition' ) ) {
						panel.collapse();
					}
				}
				section._animateChangeExpanded( function() {
					sectionTitle.trigger( 'focus' );
					content.css( 'top', '' );
					if ( args.completeCallback ) {
						args.completeCallback();
					}
				} );
				content.removeClass( 'open' );
				overlay.removeClass( 'section-open' );
				if ( section === api.state( 'expandedSection' ).get() ) {
					api.state( 'expandedSection' ).set( false );
				}
			} else {
				if ( args.completeCallback ) {
					args.completeCallback();
				}
			}
		}
	});
	api.ThemesSection = api.Section.extend(/** @lends wp.customize.ThemesSection.prototype */{
		currentTheme: '',
		overlay: '',
		template: '',
		screenshotQueue: null,
		$window: null,
		$body: null,
		loaded: 0,
		loading: false,
		fullyLoaded: false,
		term: '',
		tags: '',
		nextTerm: '',
		nextTags: '',
		filtersHeight: 0,
		headerContainer: null,
		updateCountDebounced: null,
		/**
		 * wp.customize.ThemesSection
		 *
		 * Custom section for themes that loads themes by category, and also
		 * handles the theme-details view rendering and navigation.
		 *
		 * @constructs wp.customize.ThemesSection
		 * @augments   wp.customize.Section
		 *
		 * @since 4.9.0
		 *
		 * @param {string} id - ID.
		 * @param {Object} options - Options.
		 * @return {void}
		 */
		initialize: function( id, options ) {
			var section = this;
			section.headerContainer = $();
			section.$window = $( window );
			section.$body = $( document.body );
			api.Section.prototype.initialize.call( section, id, options );
			section.updateCountDebounced = _.debounce( section.updateCount, 500 );
		},
		/**
		 * Embed the section in the DOM when the themes panel is ready.
		 *
		 * Insert the section before the themes container. Assume that a themes section is within a panel, but not necessarily the themes panel.
		 *
		 * @since 4.9.0
		 */
		embed: function() {
			var inject,
				section = this;
			// Watch for changes to the panel state.
			inject = function( panelId ) {
				var parentContainer;
				api.panel( panelId, function( panel ) {
					// The panel has been registered, wait for it to become ready/initialized.
					panel.deferred.embedded.done( function() {
						parentContainer = panel.contentContainer;
						if ( ! section.headContainer.parent().is( parentContainer ) ) {
							parentContainer.find( '.customize-themes-full-container-container' ).before( section.headContainer );
						}
						if ( ! section.contentContainer.parent().is( section.headContainer ) ) {
							section.containerParent.append( section.contentContainer );
						}
						section.deferred.embedded.resolve();
					});
				} );
			};
			section.panel.bind( inject );
			inject( section.panel.get() ); // Since a section may never get a panel, assume that it won't ever get one.
		},
		/**
		 * Set up.
		 *
		 * @since 4.2.0
		 *
		 * @return {void}
		 */
		ready: function() {
			var section = this;
			section.overlay = section.container.find( '.theme-overlay' );
			section.template = wp.template( 'customize-themes-details-view' );
			// Bind global keyboard events.
			section.container.on( 'keydown', function( event ) {
				if ( ! section.overlay.find( '.theme-wrap' ).is( ':visible' ) ) {
					return;
				}
				// Pressing the right arrow key fires a theme:next event.
				if ( 39 === event.keyCode ) {
					section.nextTheme();
				}
				// Pressing the left arrow key fires a theme:previous event.
				if ( 37 === event.keyCode ) {
					section.previousTheme();
				}
				// Pressing the escape key fires a theme:collapse event.
				if ( 27 === event.keyCode ) {
					if ( section.$body.hasClass( 'modal-open' ) ) {
						// Escape from the details modal.
						section.closeDetails();
					} else {
						// Escape from the infinite scroll list.
						section.headerContainer.find( '.customize-themes-section-title' ).focus();
					}
					event.stopPropagation(); // Prevent section from being collapsed.
				}
			});
			section.renderScreenshots = _.throttle( section.renderScreenshots, 100 );
			_.bindAll( section, 'renderScreenshots', 'loadMore', 'checkTerm', 'filtersChecked' );
		},
		/**
		 * Override Section.isContextuallyActive method.
		 *
		 * Ignore the active states' of the contained theme controls, and just
		 * use the section's own active state instead. This prevents empty search
		 * results for theme sections from causing the section to become inactive.
		 *
		 * @since 4.2.0
		 *
		 * @return {boolean}
		 */
		isContextuallyActive: function () {
			return this.active();
		},
		/**
		 * Attach events.
		 *
		 * @since 4.2.0
		 *
		 * @return {void}
		 */
		attachEvents: function () {
			var section = this, debounced;
			// Expand/Collapse accordion sections on click.
			section.container.find( '.customize-section-back' ).on( 'click keydown', function( event ) {
				if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
					return;
				}
				event.preventDefault(); // Keep this AFTER the key filter above.
				section.collapse();
			});
			section.headerContainer = $( '#accordion-section-' + section.id );
			// Expand section/panel. Only collapse when opening another section.
			section.headerContainer.on( 'click', '.customize-themes-section-title', function() {
				// Toggle accordion filters under section headers.
				if ( section.headerContainer.find( '.filter-details' ).length ) {
					section.headerContainer.find( '.customize-themes-section-title' )
						.toggleClass( 'details-open' )
						.attr( 'aria-expanded', function( i, attr ) {
							return 'true' === attr ? 'false' : 'true';
						});
					section.headerContainer.find( '.filter-details' ).slideToggle( 180 );
				}
				// Open the section.
				if ( ! section.expanded() ) {
					section.expand();
				}
			});
			// Preview installed themes.
			section.container.on( 'click', '.theme-actions .preview-theme', function() {
				api.panel( 'themes' ).loadThemePreview( $( this ).data( 'slug' ) );
			});
			// Theme navigation in details view.
			section.container.on( 'click', '.left', function() {
				section.previousTheme();
			});
			section.container.on( 'click', '.right', function() {
				section.nextTheme();
			});
			section.container.on( 'click', '.theme-backdrop, .close', function() {
				section.closeDetails();
			});
			if ( 'local' === section.params.filter_type ) {
				// Filter-search all theme objects loaded in the section.
				section.container.on( 'input', '.wp-filter-search-themes', function( event ) {
					section.filterSearch( event.currentTarget.value );
				});
			} else if ( 'remote' === section.params.filter_type ) {
				// Event listeners for remote queries with user-entered terms.
				// Search terms.
				debounced = _.debounce( section.checkTerm, 500 ); // Wait until there is no input for 500 milliseconds to initiate a search.
				section.contentContainer.on( 'input', '.wp-filter-search', function() {
					if ( ! api.panel( 'themes' ).expanded() ) {
						return;
					}
					debounced( section );
					if ( ! section.expanded() ) {
						section.expand();
					}
				});
				// Feature filters.
				section.contentContainer.on( 'click', '.filter-group input', function() {
					section.filtersChecked();
					section.checkTerm( section );
				});
			}
			// Toggle feature filters.
			section.contentContainer.on( 'click', '.feature-filter-toggle', function( e ) {
				var $themeContainer = $( '.customize-themes-full-container' ),
					$filterToggle = $( e.currentTarget );
				section.filtersHeight = $filterToggle.parents( '.themes-filter-bar' ).next( '.filter-drawer' ).height();
				if ( 0 < $themeContainer.scrollTop() ) {
					$themeContainer.animate( { scrollTop: 0 }, 400 );
					if ( $filterToggle.hasClass( 'open' ) ) {
						return;
					}
				}
				$filterToggle
					.toggleClass( 'open' )
					.attr( 'aria-expanded', function( i, attr ) {
						return 'true' === attr ? 'false' : 'true';
					})
					.parents( '.themes-filter-bar' ).next( '.filter-drawer' ).slideToggle( 180, 'linear' );
				if ( $filterToggle.hasClass( 'open' ) ) {
					var marginOffset = 1018 < window.innerWidth ? 50 : 76;
					section.contentContainer.find( '.themes' ).css( 'margin-top', section.filtersHeight + marginOffset );
				} else {
					section.contentContainer.find( '.themes' ).css( 'margin-top', 0 );
				}
			});
			// Setup section cross-linking.
			section.contentContainer.on( 'click', '.no-themes-local .search-dotorg-themes', function() {
				api.section( 'wporg_themes' ).focus();
			});
			function updateSelectedState() {
				var el = section.headerContainer.find( '.customize-themes-section-title' );
				el.toggleClass( 'selected', section.expanded() );
				el.attr( 'aria-expanded', section.expanded() ? 'true' : 'false' );
				if ( ! section.expanded() ) {
					el.removeClass( 'details-open' );
				}
			}
			section.expanded.bind( updateSelectedState );
			updateSelectedState();
			// Move section controls to the themes area.
			api.bind( 'ready', function () {
				section.contentContainer = section.container.find( '.customize-themes-section' );
				section.contentContainer.appendTo( $( '.customize-themes-full-container' ) );
				section.container.add( section.headerContainer );
			});
		},
		/**
		 * Update UI to reflect expanded state
		 *
		 * @since 4.2.0
		 *
		 * @param {boolean}  expanded
		 * @param {Object}   args
		 * @param {boolean}  args.unchanged
		 * @param {Function} args.completeCallback
		 * @return {void}
		 */
		onChangeExpanded: function ( expanded, args ) {
			// Note: there is a second argument 'args' passed.
			var section = this,
				container = section.contentContainer.closest( '.customize-themes-full-container' );
			// Immediately call the complete callback if there were no changes.
			if ( args.unchanged ) {
				if ( args.completeCallback ) {
					args.completeCallback();
				}
				return;
			}
			function expand() {
				// Try to load controls if none are loaded yet.
				if ( 0 === section.loaded ) {
					section.loadThemes();
				}
				// Collapse any sibling sections/panels.
				api.section.each( function ( otherSection ) {
					var searchTerm;
					if ( otherSection !== section ) {
						// Try to sync the current search term to the new section.
						if ( 'themes' === otherSection.params.type ) {
							searchTerm = otherSection.contentContainer.find( '.wp-filter-search' ).val();
							section.contentContainer.find( '.wp-filter-search' ).val( searchTerm );
							// Directly initialize an empty remote search to avoid a race condition.
							if ( '' === searchTerm && '' !== section.term && 'local' !== section.params.filter_type ) {
								section.term = '';
								section.initializeNewQuery( section.term, section.tags );
							} else {
								if ( 'remote' === section.params.filter_type ) {
									section.checkTerm( section );
								} else if ( 'local' === section.params.filter_type ) {
									section.filterSearch( searchTerm );
								}
							}
							otherSection.collapse( { duration: args.duration } );
						}
					}
				});
				section.contentContainer.addClass( 'current-section' );
				container.scrollTop();
				container.on( 'scroll', _.throttle( section.renderScreenshots, 300 ) );
				container.on( 'scroll', _.throttle( section.loadMore, 300 ) );
				if ( args.completeCallback ) {
					args.completeCallback();
				}
				section.updateCount(); // Show this section's count.
			}
			if ( expanded ) {
				if ( section.panel() && api.panel.has( section.panel() ) ) {
					api.panel( section.panel() ).expand({
						duration: args.duration,
						completeCallback: expand
					});
				} else {
					expand();
				}
			} else {
				section.contentContainer.removeClass( 'current-section' );
				// Always hide, even if they don't exist or are already hidden.
				section.headerContainer.find( '.filter-details' ).slideUp( 180 );
				container.off( 'scroll' );
				if ( args.completeCallback ) {
					args.completeCallback();
				}
			}
		},
		/**
		 * Return the section's content element without detaching from the parent.
		 *
		 * @since 4.9.0
		 *
		 * @return {jQuery}
		 */
		getContent: function() {
			return this.container.find( '.control-section-content' );
		},
		/**
		 * Load theme data via Ajax and add themes to the section as controls.
		 *
		 * @since 4.9.0
		 *
		 * @return {void}
		 */
		loadThemes: function() {
			var section = this, params, page, request;
			if ( section.loading ) {
				return; // We're already loading a batch of themes.
			}
			// Parameters for every API query. Additional params are set in PHP.
			page = Math.ceil( section.loaded / 100 ) + 1;
			params = {
				'nonce': api.settings.nonce.switch_themes,
				'wp_customize': 'on',
				'theme_action': section.params.action,
				'customized_theme': api.settings.theme.stylesheet,
				'page': page
			};
			// Add fields for remote filtering.
			if ( 'remote' === section.params.filter_type ) {
				params.search = section.term;
				params.tags = section.tags;
			}
			// Load themes.
			section.headContainer.closest( '.wp-full-overlay' ).addClass( 'loading' );
			section.loading = true;
			section.container.find( '.no-themes' ).hide();
			request = wp.ajax.post( 'customize_load_themes', params );
			request.done(function( data ) {
				var themes = data.themes;
				// Stop and try again if the term changed while loading.
				if ( '' !== section.nextTerm || '' !== section.nextTags ) {
					if ( section.nextTerm ) {
						section.term = section.nextTerm;
					}
					if ( section.nextTags ) {
						section.tags = section.nextTags;
					}
					section.nextTerm = '';
					section.nextTags = '';
					section.loading = false;
					section.loadThemes();
					return;
				}
				if ( 0 !== themes.length ) {
					section.loadControls( themes, page );
					if ( 1 === page ) {
						// Pre-load the first 3 theme screenshots.
						_.each( section.controls().slice( 0, 3 ), function( control ) {
							var img, src = control.params.theme.screenshot[0];
							if ( src ) {
								img = new Image();
								img.src = src;
							}
						});
						if ( 'local' !== section.params.filter_type ) {
							wp.a11y.speak( api.settings.l10n.themeSearchResults.replace( '%d', data.info.results ) );
						}
					}
					_.delay( section.renderScreenshots, 100 ); // Wait for the controls to become visible.
					if ( 'local' === section.params.filter_type || 100 > themes.length ) {
						// If we have less than the requested 100 themes, it's the end of the list.
						section.fullyLoaded = true;
					}
				} else {
					if ( 0 === section.loaded ) {
						section.container.find( '.no-themes' ).show();
						wp.a11y.speak( section.container.find( '.no-themes' ).text() );
					} else {
						section.fullyLoaded = true;
					}
				}
				if ( 'local' === section.params.filter_type ) {
					section.updateCount(); // Count of visible theme controls.
				} else {
					section.updateCount( data.info.results ); // Total number of results including pages not yet loaded.
				}
				section.container.find( '.unexpected-error' ).hide(); // Hide error notice in case it was previously shown.
				// This cannot run on request.always, as section.loading may turn false before the new controls load in the success case.
				section.headContainer.closest( '.wp-full-overlay' ).removeClass( 'loading' );
				section.loading = false;
			});
			request.fail(function( data ) {
				if ( 'undefined' === typeof data ) {
					section.container.find( '.unexpected-error' ).show();
					wp.a11y.speak( section.container.find( '.unexpected-error' ).text() );
				} else if ( 'undefined' !== typeof console && console.error ) {
					console.error( data );
				}
				// This cannot run on request.always, as section.loading may turn false before the new controls load in the success case.
				section.headContainer.closest( '.wp-full-overlay' ).removeClass( 'loading' );
				section.loading = false;
			});
		},
		/**
		 * Loads controls into the section from data received from loadThemes().
		 *
		 * @since 4.9.0
		 * @param {Array}  themes - Array of theme data to create controls with.
		 * @param {number} page   - Page of results being loaded.
		 * @return {void}
		 */
		loadControls: function( themes, page ) {
			var newThemeControls = [],
				section = this;
			// Add controls for each theme.
			_.each( themes, function( theme ) {
				var themeControl = new api.controlConstructor.theme( section.params.action + '_theme_' + theme.id, {
					type: 'theme',
					section: section.params.id,
					theme: theme,
					priority: section.loaded + 1
				} );
				api.control.add( themeControl );
				newThemeControls.push( themeControl );
				section.loaded = section.loaded + 1;
			});
			if ( 1 !== page ) {
				Array.prototype.push.apply( section.screenshotQueue, newThemeControls ); // Add new themes to the screenshot queue.
			}
		},
		/**
		 * Determines whether more themes should be loaded, and loads them.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		loadMore: function() {
			var section = this, container, bottom, threshold;
			if ( ! section.fullyLoaded && ! section.loading ) {
				container = section.container.closest( '.customize-themes-full-container' );
				bottom = container.scrollTop() + container.height();
				// Use a fixed distance to the bottom of loaded results to avoid unnecessarily
				// loading results sooner when using a percentage of scroll distance.
				threshold = container.prop( 'scrollHeight' ) - 3000;
				if ( bottom > threshold ) {
					section.loadThemes();
				}
			}
		},
		/**
		 * Event handler for search input that filters visible controls.
		 *
		 * @since 4.9.0
		 *
		 * @param {string} term - The raw search input value.
		 * @return {void}
		 */
		filterSearch: function( term ) {
			var count = 0,
				visible = false,
				section = this,
				noFilter = ( api.section.has( 'wporg_themes' ) && 'remote' !== section.params.filter_type ) ? '.no-themes-local' : '.no-themes',
				controls = section.controls(),
				terms;
			if ( section.loading ) {
				return;
			}
			// Standardize search term format and split into an array of individual words.
			terms = term.toLowerCase().trim().replace( /-/g, ' ' ).split( ' ' );
			_.each( controls, function( control ) {
				visible = control.filter( terms ); // Shows/hides and sorts control based on the applicability of the search term.
				if ( visible ) {
					count = count + 1;
				}
			});
			if ( 0 === count ) {
				section.container.find( noFilter ).show();
				wp.a11y.speak( section.container.find( noFilter ).text() );
			} else {
				section.container.find( noFilter ).hide();
			}
			section.renderScreenshots();
			api.reflowPaneContents();
			// Update theme count.
			section.updateCountDebounced( count );
		},
		/**
		 * Event handler for search input that determines if the terms have changed and loads new controls as needed.
		 *
		 * @since 4.9.0
		 *
		 * @param {wp.customize.ThemesSection} section - The current theme section, passed through the debouncer.
		 * @return {void}
		 */
		checkTerm: function( section ) {
			var newTerm;
			if ( 'remote' === section.params.filter_type ) {
				newTerm = section.contentContainer.find( '.wp-filter-search' ).val();
				if ( section.term !== newTerm.trim() ) {
					section.initializeNewQuery( newTerm, section.tags );
				}
			}
		},
		/**
		 * Check for filters checked in the feature filter list and initialize a new query.
		 *
		 * @since 4.9.0
		 *
		 * @return {void}
		 */
		filtersChecked: function() {
			var section = this,
			    items = section.container.find( '.filter-group' ).find( ':checkbox' ),
			    tags = [];
			_.each( items.filter( ':checked' ), function( item ) {
				tags.push( $( item ).prop( 'value' ) );
			});
			// When no filters are checked, restore initial state. Update filter count.
			if ( 0 === tags.length ) {
				tags = '';
				section.contentContainer.find( '.feature-filter-toggle .filter-count-0' ).show();
				section.contentContainer.find( '.feature-filter-toggle .filter-count-filters' ).hide();
			} else {
				section.contentContainer.find( '.feature-filter-toggle .theme-filter-count' ).text( tags.length );
				section.contentContainer.find( '.feature-filter-toggle .filter-count-0' ).hide();
				section.contentContainer.find( '.feature-filter-toggle .filter-count-filters' ).show();
			}
			// Check whether tags have changed, and either load or queue them.
			if ( ! _.isEqual( section.tags, tags ) ) {
				if ( section.loading ) {
					section.nextTags = tags;
				} else {
					if ( 'remote' === section.params.filter_type ) {
						section.initializeNewQuery( section.term, tags );
					} else if ( 'local' === section.params.filter_type ) {
						section.filterSearch( tags.join( ' ' ) );
					}
				}
			}
		},
		/**
		 * Reset the current query and load new results.
		 *
		 * @since 4.9.0
		 *
		 * @param {string} newTerm - New term.
		 * @param {Array} newTags - New tags.
		 * @return {void}
		 */
		initializeNewQuery: function( newTerm, newTags ) {
			var section = this;
			// Clear the controls in the section.
			_.each( section.controls(), function( control ) {
				control.container.remove();
				api.control.remove( control.id );
			});
			section.loaded = 0;
			section.fullyLoaded = false;
			section.screenshotQueue = null;
			// Run a new query, with loadThemes handling paging, etc.
			if ( ! section.loading ) {
				section.term = newTerm;
				section.tags = newTags;
				section.loadThemes();
			} else {
				section.nextTerm = newTerm; // This will reload from loadThemes() with the newest term once the current batch is loaded.
				section.nextTags = newTags; // This will reload from loadThemes() with the newest tags once the current batch is loaded.
			}
			if ( ! section.expanded() ) {
				section.expand(); // Expand the section if it isn't expanded.
			}
		},
		/**
		 * Render control's screenshot if the control comes into view.
		 *
		 * @since 4.2.0
		 *
		 * @return {void}
		 */
		renderScreenshots: function() {
			var section = this;
			// Fill queue initially, or check for more if empty.
			if ( null === section.screenshotQueue || 0 === section.screenshotQueue.length ) {
				// Add controls that haven't had their screenshots rendered.
				section.screenshotQueue = _.filter( section.controls(), function( control ) {
					return ! control.screenshotRendered;
				});
			}
			// Are all screenshots rendered (for now)?
			if ( ! section.screenshotQueue.length ) {
				return;
			}
			section.screenshotQueue = _.filter( section.screenshotQueue, function( control ) {
				var $imageWrapper = control.container.find( '.theme-screenshot' ),
					$image = $imageWrapper.find( 'img' );
				if ( ! $image.length ) {
					return false;
				}
				if ( $image.is( ':hidden' ) ) {
					return true;
				}
				// Based on unveil.js.
				var wt = section.$window.scrollTop(),
					wb = wt + section.$window.height(),
					et = $image.offset().top,
					ih = $imageWrapper.height(),
					eb = et + ih,
					threshold = ih * 3,
					inView = eb >= wt - threshold && et <= wb + threshold;
				if ( inView ) {
					control.container.trigger( 'render-screenshot' );
				}
				// If the image is in view return false so it's cleared from the queue.
				return ! inView;
			} );
		},
		/**
		 * Get visible count.
		 *
		 * @since 4.9.0
		 *
		 * @return {number} Visible count.
		 */
		getVisibleCount: function() {
			return this.contentContainer.find( 'li.customize-control:visible' ).length;
		},
		/**
		 * Update the number of themes in the section.
		 *
		 * @since 4.9.0
		 *
		 * @return {void}
		 */
		updateCount: function( count ) {
			var section = this, countEl, displayed;
			if ( ! count && 0 !== count ) {
				count = section.getVisibleCount();
			}
			displayed = section.contentContainer.find( '.themes-displayed' );
			countEl = section.contentContainer.find( '.theme-count' );
			if ( 0 === count ) {
				countEl.text( '0' );
			} else {
				// Animate the count change for emphasis.
				displayed.fadeOut( 180, function() {
					countEl.text( count );
					displayed.fadeIn( 180 );
				} );
				wp.a11y.speak( api.settings.l10n.announceThemeCount.replace( '%d', count ) );
			}
		},
		/**
		 * Advance the modal to the next theme.
		 *
		 * @since 4.2.0
		 *
		 * @return {void}
		 */
		nextTheme: function () {
			var section = this;
			if ( section.getNextTheme() ) {
				section.showDetails( section.getNextTheme(), function() {
					section.overlay.find( '.right' ).focus();
				} );
			}
		},
		/**
		 * Get the next theme model.
		 *
		 * @since 4.2.0
		 *
		 * @return {wp.customize.ThemeControl|boolean} Next theme.
		 */
		getNextTheme: function () {
			var section = this, control, nextControl, sectionControls, i;
			control = api.control( section.params.action + '_theme_' + section.currentTheme );
			sectionControls = section.controls();
			i = _.indexOf( sectionControls, control );
			if ( -1 === i ) {
				return false;
			}
			nextControl = sectionControls[ i + 1 ];
			if ( ! nextControl ) {
				return false;
			}
			return nextControl.params.theme;
		},
		/**
		 * Advance the modal to the previous theme.
		 *
		 * @since 4.2.0
		 * @return {void}
		 */
		previousTheme: function () {
			var section = this;
			if ( section.getPreviousTheme() ) {
				section.showDetails( section.getPreviousTheme(), function() {
					section.overlay.find( '.left' ).focus();
				} );
			}
		},
		/**
		 * Get the previous theme model.
		 *
		 * @since 4.2.0
		 * @return {wp.customize.ThemeControl|boolean} Previous theme.
		 */
		getPreviousTheme: function () {
			var section = this, control, nextControl, sectionControls, i;
			control = api.control( section.params.action + '_theme_' + section.currentTheme );
			sectionControls = section.controls();
			i = _.indexOf( sectionControls, control );
			if ( -1 === i ) {
				return false;
			}
			nextControl = sectionControls[ i - 1 ];
			if ( ! nextControl ) {
				return false;
			}
			return nextControl.params.theme;
		},
		/**
		 * Disable buttons when we're viewing the first or last theme.
		 *
		 * @since 4.2.0
		 *
		 * @return {void}
		 */
		updateLimits: function () {
			if ( ! this.getNextTheme() ) {
				this.overlay.find( '.right' ).addClass( 'disabled' );
			}
			if ( ! this.getPreviousTheme() ) {
				this.overlay.find( '.left' ).addClass( 'disabled' );
			}
		},
		/**
		 * Load theme preview.
		 *
		 * @since 4.7.0
		 * @access public
		 *
		 * @deprecated
		 * @param {string} themeId Theme ID.
		 * @return {jQuery.promise} Promise.
		 */
		loadThemePreview: function( themeId ) {
			return api.ThemesPanel.prototype.loadThemePreview.call( this, themeId );
		},
		/**
		 * Render & show the theme details for a given theme model.
		 *
		 * @since 4.2.0
		 *
		 * @param {Object} theme - Theme.
		 * @param {Function} [callback] - Callback once the details have been shown.
		 * @return {void}
		 */
		showDetails: function ( theme, callback ) {
			var section = this, panel = api.panel( 'themes' );
			section.currentTheme = theme.id;
			section.overlay.html( section.template( theme ) )
				.fadeIn( 'fast' )
				.focus();
			function disableSwitchButtons() {
				return ! panel.canSwitchTheme( theme.id );
			}
			// Temporary special function since supplying SFTP credentials does not work yet. See #42184.
			function disableInstallButtons() {
				return disableSwitchButtons() || false === api.settings.theme._canInstall || true === api.settings.theme._filesystemCredentialsNeeded;
			}
			section.overlay.find( 'button.preview, button.preview-theme' ).toggleClass( 'disabled', disableSwitchButtons() );
			section.overlay.find( 'button.theme-install' ).toggleClass( 'disabled', disableInstallButtons() );
			section.$body.addClass( 'modal-open' );
			section.containFocus( section.overlay );
			section.updateLimits();
			wp.a11y.speak( api.settings.l10n.announceThemeDetails.replace( '%s', theme.name ) );
			if ( callback ) {
				callback();
			}
		},
		/**
		 * Close the theme details modal.
		 *
		 * @since 4.2.0
		 *
		 * @return {void}
		 */
		closeDetails: function () {
			var section = this;
			section.$body.removeClass( 'modal-open' );
			section.overlay.fadeOut( 'fast' );
			api.control( section.params.action + '_theme_' + section.currentTheme ).container.find( '.theme' ).focus();
		},
		/**
		 * Keep tab focus within the theme details modal.
		 *
		 * @since 4.2.0
		 *
		 * @param {jQuery} el - Element to contain focus.
		 * @return {void}
		 */
		containFocus: function( el ) {
			var tabbables;
			el.on( 'keydown', function( event ) {
				// Return if it's not the tab key
				// When navigating with prev/next focus is already handled.
				if ( 9 !== event.keyCode ) {
					return;
				}
				// Uses jQuery UI to get the tabbable elements.
				tabbables = $( ':tabbable', el );
				// Keep focus within the overlay.
				if ( tabbables.last()[0] === event.target && ! event.shiftKey ) {
					tabbables.first().focus();
					return false;
				} else if ( tabbables.first()[0] === event.target && event.shiftKey ) {
					tabbables.last().focus();
					return false;
				}
			});
		}
	});
	api.OuterSection = api.Section.extend(/** @lends wp.customize.OuterSection.prototype */{
		/**
		 * Class wp.customize.OuterSection.
		 *
		 * Creates section outside of the sidebar, there is no ui to trigger collapse/expand so
		 * it would require custom handling.
		 *
		 * @constructs wp.customize.OuterSection
		 * @augments   wp.customize.Section
		 *
		 * @since 4.9.0
		 *
		 * @return {void}
		 */
		initialize: function() {
			var section = this;
			section.containerParent = '#customize-outer-theme-controls';
			section.containerPaneParent = '.customize-outer-pane-parent';
			api.Section.prototype.initialize.apply( section, arguments );
		},
		/**
		 * Overrides api.Section.prototype.onChangeExpanded to prevent collapse/expand effect
		 * on other sections and panels.
		 *
		 * @since 4.9.0
		 *
		 * @param {boolean}  expanded - The expanded state to transition to.
		 * @param {Object}   [args] - Args.
		 * @param {boolean}  [args.unchanged] - Whether the state is already known to not be changed, and so short-circuit with calling completeCallback early.
		 * @param {Function} [args.completeCallback] - Function to call when the slideUp/slideDown has completed.
		 * @param {Object}   [args.duration] - The duration for the animation.
		 */
		onChangeExpanded: function( expanded, args ) {
			var section = this,
				container = section.headContainer.closest( '.wp-full-overlay-sidebar-content' ),
				content = section.contentContainer,
				backBtn = content.find( '.customize-section-back' ),
				sectionTitle = section.headContainer.find( '.accordion-section-title button, .accordion-section-title[tabindex]' ).first(),
				body = $( document.body ),
				expand, panel;
			body.toggleClass( 'outer-section-open', expanded );
			section.container.toggleClass( 'open', expanded );
			section.container.removeClass( 'busy' );
			api.section.each( function( _section ) {
				if ( 'outer' === _section.params.type && _section.id !== section.id ) {
					_section.container.removeClass( 'open' );
				}
			} );
			if ( expanded && ! content.hasClass( 'open' ) ) {
				if ( args.unchanged ) {
					expand = args.completeCallback;
				} else {
					expand = function() {
						section._animateChangeExpanded( function() {
							backBtn.trigger( 'focus' );
							content.css( 'top', '' );
							container.scrollTop( 0 );
							if ( args.completeCallback ) {
								args.completeCallback();
							}
						} );
						content.addClass( 'open' );
					}.bind( this );
				}
				if ( section.panel() ) {
					api.panel( section.panel() ).expand({
						duration: args.duration,
						completeCallback: expand
					});
				} else {
					expand();
				}
			} else if ( ! expanded && content.hasClass( 'open' ) ) {
				if ( section.panel() ) {
					panel = api.panel( section.panel() );
					if ( panel.contentContainer.hasClass( 'skip-transition' ) ) {
						panel.collapse();
					}
				}
				section._animateChangeExpanded( function() {
					sectionTitle.trigger( 'focus' );
					content.css( 'top', '' );
					if ( args.completeCallback ) {
						args.completeCallback();
					}
				} );
				content.removeClass( 'open' );
			} else {
				if ( args.completeCallback ) {
					args.completeCallback();
				}
			}
		}
	});
	api.Panel = Container.extend(/** @lends wp.customize.Panel.prototype */{
		containerType: 'panel',
		/**
		 * @constructs wp.customize.Panel
		 * @augments   wp.customize~Container
		 *
		 * @since 4.1.0
		 *
		 * @param {string}  id - The ID for the panel.
		 * @param {Object}  options - Object containing one property: params.
		 * @param {string}  options.title - Title shown when panel is collapsed and expanded.
		 * @param {string}  [options.description] - Description shown at the top of the panel.
		 * @param {number}  [options.priority=100] - The sort priority for the panel.
		 * @param {string}  [options.type=default] - The type of the panel. See wp.customize.panelConstructor.
		 * @param {string}  [options.content] - The markup to be used for the panel container. If empty, a JS template is used.
		 * @param {boolean} [options.active=true] - Whether the panel is active or not.
		 * @param {Object}  [options.params] - Deprecated wrapper for the above properties.
		 */
		initialize: function ( id, options ) {
			var panel = this, params;
			params = options.params || options;
			// Look up the type if one was not supplied.
			if ( ! params.type ) {
				_.find( api.panelConstructor, function( Constructor, type ) {
					if ( Constructor === panel.constructor ) {
						params.type = type;
						return true;
					}
					return false;
				} );
			}
			Container.prototype.initialize.call( panel, id, params );
			panel.embed();
			panel.deferred.embedded.done( function () {
				panel.ready();
			});
		},
		/**
		 * Embed the container in the DOM when any parent panel is ready.
		 *
		 * @since 4.1.0
		 */
		embed: function () {
			var panel = this,
				container = $( '#customize-theme-controls' ),
				parentContainer = $( '.customize-pane-parent' ); // @todo This should be defined elsewhere, and to be configurable.
			if ( ! panel.headContainer.parent().is( parentContainer ) ) {
				parentContainer.append( panel.headContainer );
			}
			if ( ! panel.contentContainer.parent().is( panel.headContainer ) ) {
				container.append( panel.contentContainer );
			}
			panel.renderContent();
			panel.deferred.embedded.resolve();
		},
		/**
		 * @since 4.1.0
		 */
		attachEvents: function () {
			var meta, panel = this;
			// Expand/Collapse accordion sections on click.
			panel.headContainer.find( '.accordion-section-title button, .accordion-section-title[tabindex]' ).on( 'click keydown', function( event ) {
				if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
					return;
				}
				event.preventDefault(); // Keep this AFTER the key filter above.
				if ( ! panel.expanded() ) {
					panel.expand();
				}
			});
			// Close panel.
			panel.container.find( '.customize-panel-back' ).on( 'click keydown', function( event ) {
				if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
					return;
				}
				event.preventDefault(); // Keep this AFTER the key filter above.
				if ( panel.expanded() ) {
					panel.collapse();
				}
			});
			meta = panel.container.find( '.panel-meta:first' );
			meta.find( '> .accordion-section-title .customize-help-toggle' ).on( 'click', function() {
				if ( meta.hasClass( 'cannot-expand' ) ) {
					return;
				}
				var content = meta.find( '.customize-panel-description:first' );
				if ( meta.hasClass( 'open' ) ) {
					meta.toggleClass( 'open' );
					content.slideUp( panel.defaultExpandedArguments.duration, function() {
						content.trigger( 'toggled' );
					} );
					$( this ).attr( 'aria-expanded', false );
				} else {
					content.slideDown( panel.defaultExpandedArguments.duration, function() {
						content.trigger( 'toggled' );
					} );
					meta.toggleClass( 'open' );
					$( this ).attr( 'aria-expanded', true );
				}
			});
		},
		/**
		 * Get the sections that are associated with this panel, sorted by their priority Value.
		 *
		 * @since 4.1.0
		 *
		 * @return {Array}
		 */
		sections: function () {
			return this._children( 'panel', 'section' );
		},
		/**
		 * Return whether this panel has any active sections.
		 *
		 * @since 4.1.0
		 *
		 * @return {boolean} Whether contextually active.
		 */
		isContextuallyActive: function () {
			var panel = this,
				sections = panel.sections(),
				activeCount = 0;
			_( sections ).each( function ( section ) {
				if ( section.active() && section.isContextuallyActive() ) {
					activeCount += 1;
				}
			} );
			return ( activeCount !== 0 );
		},
		/**
		 * Update UI to reflect expanded state.
		 *
		 * @since 4.1.0
		 *
		 * @param {boolean}  expanded
		 * @param {Object}   args
		 * @param {boolean}  args.unchanged
		 * @param {Function} args.completeCallback
		 * @return {void}
		 */
		onChangeExpanded: function ( expanded, args ) {
			// Immediately call the complete callback if there were no changes.
			if ( args.unchanged ) {
				if ( args.completeCallback ) {
					args.completeCallback();
				}
				return;
			}
			// Note: there is a second argument 'args' passed.
			var panel = this,
				accordionSection = panel.contentContainer,
				overlay = accordionSection.closest( '.wp-full-overlay' ),
				container = accordionSection.closest( '.wp-full-overlay-sidebar-content' ),
				topPanel = panel.headContainer.find( '.accordion-section-title button, .accordion-section-title[tabindex]' ),
				backBtn = accordionSection.find( '.customize-panel-back' ),
				childSections = panel.sections(),
				skipTransition;
			if ( expanded && ! accordionSection.hasClass( 'current-panel' ) ) {
				// Collapse any sibling sections/panels.
				api.section.each( function ( section ) {
					if ( panel.id !== section.panel() ) {
						section.collapse( { duration: 0 } );
					}
				});
				api.panel.each( function ( otherPanel ) {
					if ( panel !== otherPanel ) {
						otherPanel.collapse( { duration: 0 } );
					}
				});
				if ( panel.params.autoExpandSoleSection && 1 === childSections.length && childSections[0].active.get() ) {
					accordionSection.addClass( 'current-panel skip-transition' );
					overlay.addClass( 'in-sub-panel' );
					childSections[0].expand( {
						completeCallback: args.completeCallback
					} );
				} else {
					panel._animateChangeExpanded( function() {
						backBtn.trigger( 'focus' );
						accordionSection.css( 'top', '' );
						container.scrollTop( 0 );
						if ( args.completeCallback ) {
							args.completeCallback();
						}
					} );
					accordionSection.addClass( 'current-panel' );
					overlay.addClass( 'in-sub-panel' );
				}
				api.state( 'expandedPanel' ).set( panel );
			} else if ( ! expanded && accordionSection.hasClass( 'current-panel' ) ) {
				skipTransition = accordionSection.hasClass( 'skip-transition' );
				if ( ! skipTransition ) {
					panel._animateChangeExpanded( function() {
						topPanel.focus();
						accordionSection.css( 'top', '' );
						if ( args.completeCallback ) {
							args.completeCallback();
						}
					} );
				} else {
					accordionSection.removeClass( 'skip-transition' );
				}
				overlay.removeClass( 'in-sub-panel' );
				accordionSection.removeClass( 'current-panel' );
				if ( panel === api.state( 'expandedPanel' ).get() ) {
					api.state( 'expandedPanel' ).set( false );
				}
			}
		},
		/**
		 * Render the panel from its JS template, if it exists.
		 *
		 * The panel's container must already exist in the DOM.
		 *
		 * @since 4.3.0
		 */
		renderContent: function () {
			var template,
				panel = this;
			// Add the content to the container.
			if ( 0 !== $( '#tmpl-' + panel.templateSelector + '-content' ).length ) {
				template = wp.template( panel.templateSelector + '-content' );
			} else {
				template = wp.template( 'customize-panel-default-content' );
			}
			if ( template && panel.headContainer ) {
				panel.contentContainer.html( template( _.extend(
					{ id: panel.id },
					panel.params
				) ) );
			}
		}
	});
	api.ThemesPanel = api.Panel.extend(/** @lends wp.customize.ThemsPanel.prototype */{
		/**
		 *  Class wp.customize.ThemesPanel.
		 *
		 * Custom section for themes that displays without the customize preview.
		 *
		 * @constructs wp.customize.ThemesPanel
		 * @augments   wp.customize.Panel
		 *
		 * @since 4.9.0
		 *
		 * @param {string} id - The ID for the panel.
		 * @param {Object} options - Options.
		 * @return {void}
		 */
		initialize: function( id, options ) {
			var panel = this;
			panel.installingThemes = [];
			api.Panel.prototype.initialize.call( panel, id, options );
		},
		/**
		 * Determine whether a given theme can be switched to, or in general.
		 *
		 * @since 4.9.0
		 *
		 * @param {string} [slug] - Theme slug.
		 * @return {boolean} Whether the theme can be switched to.
		 */
		canSwitchTheme: function canSwitchTheme( slug ) {
			if ( slug && slug === api.settings.theme.stylesheet ) {
				return true;
			}
			return 'publish' === api.state( 'selectedChangesetStatus' ).get() && ( '' === api.state( 'changesetStatus' ).get() || 'auto-draft' === api.state( 'changesetStatus' ).get() );
		},
		/**
		 * Attach events.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		attachEvents: function() {
			var panel = this;
			// Attach regular panel events.
			api.Panel.prototype.attachEvents.apply( panel );
			// Temporary since supplying SFTP credentials does not work yet. See #42184.
			if ( api.settings.theme._canInstall && api.settings.theme._filesystemCredentialsNeeded ) {
				panel.notifications.add( new api.Notification( 'theme_install_unavailable', {
					message: api.l10n.themeInstallUnavailable,
					type: 'info',
					dismissible: true
				} ) );
			}
			function toggleDisabledNotifications() {
				if ( panel.canSwitchTheme() ) {
					panel.notifications.remove( 'theme_switch_unavailable' );
				} else {
					panel.notifications.add( new api.Notification( 'theme_switch_unavailable', {
						message: api.l10n.themePreviewUnavailable,
						type: 'warning'
					} ) );
				}
			}
			toggleDisabledNotifications();
			api.state( 'selectedChangesetStatus' ).bind( toggleDisabledNotifications );
			api.state( 'changesetStatus' ).bind( toggleDisabledNotifications );
			// Collapse panel to customize the current theme.
			panel.contentContainer.on( 'click', '.customize-theme', function() {
				panel.collapse();
			});
			// Toggle between filtering and browsing themes on mobile.
			panel.contentContainer.on( 'click', '.customize-themes-section-title, .customize-themes-mobile-back', function() {
				$( '.wp-full-overlay' ).toggleClass( 'showing-themes' );
			});
			// Install (and maybe preview) a theme.
			panel.contentContainer.on( 'click', '.theme-install', function( event ) {
				panel.installTheme( event );
			});
			// Update a theme. Theme cards have the class, the details modal has the id.
			panel.contentContainer.on( 'click', '.update-theme, #update-theme', function( event ) {
				// #update-theme is a link.
				event.preventDefault();
				event.stopPropagation();
				panel.updateTheme( event );
			});
			// Delete a theme.
			panel.contentContainer.on( 'click', '.delete-theme', function( event ) {
				panel.deleteTheme( event );
			});
			_.bindAll( panel, 'installTheme', 'updateTheme' );
		},
		/**
		 * Update UI to reflect expanded state
		 *
		 * @since 4.9.0
		 *
		 * @param {boolean}  expanded - Expanded state.
		 * @param {Object}   args - Args.
		 * @param {boolean}  args.unchanged - Whether or not the state changed.
		 * @param {Function} args.completeCallback - Callback to execute when the animation completes.
		 * @return {void}
		 */
		onChangeExpanded: function( expanded, args ) {
			var panel = this, overlay, sections, hasExpandedSection = false;
			// Expand/collapse the panel normally.
			api.Panel.prototype.onChangeExpanded.apply( this, [ expanded, args ] );
			// Immediately call the complete callback if there were no changes.
			if ( args.unchanged ) {
				if ( args.completeCallback ) {
					args.completeCallback();
				}
				return;
			}
			overlay = panel.headContainer.closest( '.wp-full-overlay' );
			if ( expanded ) {
				overlay
					.addClass( 'in-themes-panel' )
					.delay( 200 ).find( '.customize-themes-full-container' ).addClass( 'animate' );
				_.delay( function() {
					overlay.addClass( 'themes-panel-expanded' );
				}, 200 );
				// Automatically open the first section (except on small screens), if one isn't already expanded.
				if ( 600 < window.innerWidth ) {
					sections = panel.sections();
					_.each( sections, function( section ) {
						if ( section.expanded() ) {
							hasExpandedSection = true;
						}
					} );
					if ( ! hasExpandedSection && sections.length > 0 ) {
						sections[0].expand();
					}
				}
			} else {
				overlay
					.removeClass( 'in-themes-panel themes-panel-expanded' )
					.find( '.customize-themes-full-container' ).removeClass( 'animate' );
			}
		},
		/**
		 * Install a theme via wp.updates.
		 *
		 * @since 4.9.0
		 *
		 * @param {jQuery.Event} event - Event.
		 * @return {jQuery.promise} Promise.
		 */
		installTheme: function( event ) {
			var panel = this, preview, onInstallSuccess, slug = $( event.target ).data( 'slug' ), deferred = $.Deferred(), request;
			preview = $( event.target ).hasClass( 'preview' );
			// Temporary since supplying SFTP credentials does not work yet. See #42184.
			if ( api.settings.theme._filesystemCredentialsNeeded ) {
				deferred.reject({
					errorCode: 'theme_install_unavailable'
				});
				return deferred.promise();
			}
			// Prevent loading a non-active theme preview when there is a drafted/scheduled changeset.
			if ( ! panel.canSwitchTheme( slug ) ) {
				deferred.reject({
					errorCode: 'theme_switch_unavailable'
				});
				return deferred.promise();
			}
			// Theme is already being installed.
			if ( _.contains( panel.installingThemes, slug ) ) {
				deferred.reject({
					errorCode: 'theme_already_installing'
				});
				return deferred.promise();
			}
			wp.updates.maybeRequestFilesystemCredentials( event );
			onInstallSuccess = function( response ) {
				var theme = false, themeControl;
				if ( preview ) {
					api.notifications.remove( 'theme_installing' );
					panel.loadThemePreview( slug );
				} else {
					api.control.each( function( control ) {
						if ( 'theme' === control.params.type && control.params.theme.id === response.slug ) {
							theme = control.params.theme; // Used below to add theme control.
							control.rerenderAsInstalled( true );
						}
					});
					// Don't add the same theme more than once.
					if ( ! theme || api.control.has( 'installed_theme_' + theme.id ) ) {
						deferred.resolve( response );
						return;
					}
					// Add theme control to installed section.
					theme.type = 'installed';
					themeControl = new api.controlConstructor.theme( 'installed_theme_' + theme.id, {
						type: 'theme',
						section: 'installed_themes',
						theme: theme,
						priority: 0 // Add all newly-installed themes to the top.
					} );
					api.control.add( themeControl );
					api.control( themeControl.id ).container.trigger( 'render-screenshot' );
					// Close the details modal if it's open to the installed theme.
					api.section.each( function( section ) {
						if ( 'themes' === section.params.type ) {
							if ( theme.id === section.currentTheme ) { // Don't close the modal if the user has navigated elsewhere.
								section.closeDetails();
							}
						}
					});
				}
				deferred.resolve( response );
			};
			panel.installingThemes.push( slug ); // Note: we don't remove elements from installingThemes, since they shouldn't be installed again.
			request = wp.updates.installTheme( {
				slug: slug
			} );
			// Also preview the theme as the event is triggered on Install & Preview.
			if ( preview ) {
				api.notifications.add( new api.OverlayNotification( 'theme_installing', {
					message: api.l10n.themeDownloading,
					type: 'info',
					loading: true
				} ) );
			}
			request.done( onInstallSuccess );
			request.fail( function() {
				api.notifications.remove( 'theme_installing' );
			} );
			return deferred.promise();
		},
		/**
		 * Load theme preview.
		 *
		 * @since 4.9.0
		 *
		 * @param {string} themeId Theme ID.
		 * @return {jQuery.promise} Promise.
		 */
		loadThemePreview: function( themeId ) {
			var panel = this, deferred = $.Deferred(), onceProcessingComplete, urlParser, queryParams;
			// Prevent loading a non-active theme preview when there is a drafted/scheduled changeset.
			if ( ! panel.canSwitchTheme( themeId ) ) {
				deferred.reject({
					errorCode: 'theme_switch_unavailable'
				});
				return deferred.promise();
			}
			urlParser = document.createElement( 'a' );
			urlParser.href = location.href;
			queryParams = _.extend(
				api.utils.parseQueryString( urlParser.search.substr( 1 ) ),
				{
					theme: themeId,
					changeset_uuid: api.settings.changeset.uuid,
					'return': api.settings.url['return']
				}
			);
			// Include autosaved param to load autosave revision without prompting user to restore it.
			if ( ! api.state( 'saved' ).get() ) {
				queryParams.customize_autosaved = 'on';
			}
			urlParser.search = $.param( queryParams );
			// Update loading message. Everything else is handled by reloading the page.
			api.notifications.add( new api.OverlayNotification( 'theme_previewing', {
				message: api.l10n.themePreviewWait,
				type: 'info',
				loading: true
			} ) );
			onceProcessingComplete = function() {
				var request;
				if ( api.state( 'processing' ).get() > 0 ) {
					return;
				}
				api.state( 'processing' ).unbind( onceProcessingComplete );
				request = api.requestChangesetUpdate( {}, { autosave: true } );
				request.done( function() {
					deferred.resolve();
					$( window ).off( 'beforeunload.customize-confirm' );
					location.replace( urlParser.href );
				} );
				request.fail( function() {
					// @todo Show notification regarding failure.
					api.notifications.remove( 'theme_previewing' );
					deferred.reject();
				} );
			};
			if ( 0 === api.state( 'processing' ).get() ) {
				onceProcessingComplete();
			} else {
				api.state( 'processing' ).bind( onceProcessingComplete );
			}
			return deferred.promise();
		},
		/**
		 * Update a theme via wp.updates.
		 *
		 * @since 4.9.0
		 *
		 * @param {jQuery.Event} event - Event.
		 * @return {void}
		 */
		updateTheme: function( event ) {
			wp.updates.maybeRequestFilesystemCredentials( event );
			$( document ).one( 'wp-theme-update-success', function( e, response ) {
				// Rerender the control to reflect the update.
				api.control.each( function( control ) {
					if ( 'theme' === control.params.type && control.params.theme.id === response.slug ) {
						control.params.theme.hasUpdate = false;
						control.params.theme.version = response.newVersion;
						setTimeout( function() {
							control.rerenderAsInstalled( true );
						}, 2000 );
					}
				});
			} );
			wp.updates.updateTheme( {
				slug: $( event.target ).closest( '.notice' ).data( 'slug' )
			} );
		},
		/**
		 * Delete a theme via wp.updates.
		 *
		 * @since 4.9.0
		 *
		 * @param {jQuery.Event} event - Event.
		 * @return {void}
		 */
		deleteTheme: function( event ) {
			var theme, section;
			theme = $( event.target ).data( 'slug' );
			section = api.section( 'installed_themes' );
			event.preventDefault();
			// Temporary since supplying SFTP credentials does not work yet. See #42184.
			if ( api.settings.theme._filesystemCredentialsNeeded ) {
				return;
			}
			// Confirmation dialog for deleting a theme.
			if ( ! window.confirm( api.settings.l10n.confirmDeleteTheme ) ) {
				return;
			}
			wp.updates.maybeRequestFilesystemCredentials( event );
			$( document ).one( 'wp-theme-delete-success', function() {
				var control = api.control( 'installed_theme_' + theme );
				// Remove theme control.
				control.container.remove();
				api.control.remove( control.id );
				// Update installed count.
				section.loaded = section.loaded - 1;
				section.updateCount();
				// Rerender any other theme controls as uninstalled.
				api.control.each( function( control ) {
					if ( 'theme' === control.params.type && control.params.theme.id === theme ) {
						control.rerenderAsInstalled( false );
					}
				});
			} );
			wp.updates.deleteTheme( {
				slug: theme
			} );
			// Close modal and focus the section.
			section.closeDetails();
			section.focus();
		}
	});
	api.Control = api.Class.extend(/** @lends wp.customize.Control.prototype */{
		defaultActiveArguments: { duration: 'fast', completeCallback: $.noop },
		/**
		 * Default params.
		 *
		 * @since 4.9.0
		 * @var {object}
		 */
		defaults: {
			label: '',
			description: '',
			active: true,
			priority: 10
		},
		/**
		 * A Customizer Control.
		 *
		 * A control provides a UI element that allows a user to modify a Customizer Setting.
		 *
		 * @see PHP class WP_Customize_Control.
		 *
		 * @constructs wp.customize.Control
		 * @augments   wp.customize.Class
		 *
		 * @borrows wp.customize~focus as this#focus
		 * @borrows wp.customize~Container#activate as this#activate
		 * @borrows wp.customize~Container#deactivate as this#deactivate
		 * @borrows wp.customize~Container#_toggleActive as this#_toggleActive
		 *
		 * @param {string} id                       - Unique identifier for the control instance.
		 * @param {Object} options                  - Options hash for the control instance.
		 * @param {Object} options.type             - Type of control (e.g. text, radio, dropdown-pages, etc.)
		 * @param {string} [options.content]        - The HTML content for the control or at least its container. This should normally be left blank and instead supplying a templateId.
		 * @param {string} [options.templateId]     - Template ID for control's content.
		 * @param {string} [options.priority=10]    - Order of priority to show the control within the section.
		 * @param {string} [options.active=true]    - Whether the control is active.
		 * @param {string} options.section          - The ID of the section the control belongs to.
		 * @param {mixed}  [options.setting]        - The ID of the main setting or an instance of this setting.
		 * @param {mixed}  options.settings         - An object with keys (e.g. default) that maps to setting IDs or Setting/Value objects, or an array of setting IDs or Setting/Value objects.
		 * @param {mixed}  options.settings.default - The ID of the setting the control relates to.
		 * @param {string} options.settings.data    - @todo Is this used?
		 * @param {string} options.label            - Label.
		 * @param {string} options.description      - Description.
		 * @param {number} [options.instanceNumber] - Order in which this instance was created in relation to other instances.
		 * @param {Object} [options.params]         - Deprecated wrapper for the above properties.
		 * @return {void}
		 */
		initialize: function( id, options ) {
			var control = this, deferredSettingIds = [], settings, gatherSettings;
			control.params = _.extend(
				{},
				control.defaults,
				control.params || {}, // In case subclass already defines.
				options.params || options || {} // The options.params property is deprecated, but it is checked first for back-compat.
			);
			if ( ! api.Control.instanceCounter ) {
				api.Control.instanceCounter = 0;
			}
			api.Control.instanceCounter++;
			if ( ! control.params.instanceNumber ) {
				control.params.instanceNumber = api.Control.instanceCounter;
			}
			// Look up the type if one was not supplied.
			if ( ! control.params.type ) {
				_.find( api.controlConstructor, function( Constructor, type ) {
					if ( Constructor === control.constructor ) {
						control.params.type = type;
						return true;
					}
					return false;
				} );
			}
			if ( ! control.params.content ) {
				control.params.content = $( '', {
					id: 'customize-control-' + id.replace( /]/g, '' ).replace( /\[/g, '-' ),
					'class': 'customize-control customize-control-' + control.params.type
				} );
			}
			control.id = id;
			control.selector = '#customize-control-' + id.replace( /\]/g, '' ).replace( /\[/g, '-' ); // Deprecated, likely dead code from time before #28709.
			if ( control.params.content ) {
				control.container = $( control.params.content );
			} else {
				control.container = $( control.selector ); // Likely dead, per above. See #28709.
			}
			if ( control.params.templateId ) {
				control.templateSelector = control.params.templateId;
			} else {
				control.templateSelector = 'customize-control-' + control.params.type + '-content';
			}
			control.deferred = _.extend( control.deferred || {}, {
				embedded: new $.Deferred()
			} );
			control.section = new api.Value();
			control.priority = new api.Value();
			control.active = new api.Value();
			control.activeArgumentsQueue = [];
			control.notifications = new api.Notifications({
				alt: control.altNotice
			});
			control.elements = [];
			control.active.bind( function ( active ) {
				var args = control.activeArgumentsQueue.shift();
				args = $.extend( {}, control.defaultActiveArguments, args );
				control.onChangeActive( active, args );
			} );
			control.section.set( control.params.section );
			control.priority.set( isNaN( control.params.priority ) ? 10 : control.params.priority );
			control.active.set( control.params.active );
			api.utils.bubbleChildValueChanges( control, [ 'section', 'priority', 'active' ] );
			control.settings = {};
			settings = {};
			if ( control.params.setting ) {
				settings['default'] = control.params.setting;
			}
			_.extend( settings, control.params.settings );
			// Note: Settings can be an array or an object, with values being either setting IDs or Setting (or Value) objects.
			_.each( settings, function( value, key ) {
				var setting;
				if ( _.isObject( value ) && _.isFunction( value.extended ) && value.extended( api.Value ) ) {
					control.settings[ key ] = value;
				} else if ( _.isString( value ) ) {
					setting = api( value );
					if ( setting ) {
						control.settings[ key ] = setting;
					} else {
						deferredSettingIds.push( value );
					}
				}
			} );
			gatherSettings = function() {
				// Fill-in all resolved settings.
				_.each( settings, function ( settingId, key ) {
					if ( ! control.settings[ key ] && _.isString( settingId ) ) {
						control.settings[ key ] = api( settingId );
					}
				} );
				// Make sure settings passed as array gets associated with default.
				if ( control.settings[0] && ! control.settings['default'] ) {
					control.settings['default'] = control.settings[0];
				}
				// Identify the main setting.
				control.setting = control.settings['default'] || null;
				control.linkElements(); // Link initial elements present in server-rendered content.
				control.embed();
			};
			if ( 0 === deferredSettingIds.length ) {
				gatherSettings();
			} else {
				api.apply( api, deferredSettingIds.concat( gatherSettings ) );
			}
			// After the control is embedded on the page, invoke the "ready" method.
			control.deferred.embedded.done( function () {
				control.linkElements(); // Link any additional elements after template is rendered by renderContent().
				control.setupNotifications();
				control.ready();
			});
		},
		/**
		 * Link elements between settings and inputs.
		 *
		 * @since 4.7.0
		 * @access public
		 *
		 * @return {void}
		 */
		linkElements: function () {
			var control = this, nodes, radios, element;
			nodes = control.container.find( '[data-customize-setting-link], [data-customize-setting-key-link]' );
			radios = {};
			nodes.each( function () {
				var node = $( this ), name, setting;
				if ( node.data( 'customizeSettingLinked' ) ) {
					return;
				}
				node.data( 'customizeSettingLinked', true ); // Prevent re-linking element.
				if ( node.is( ':radio' ) ) {
					name = node.prop( 'name' );
					if ( radios[name] ) {
						return;
					}
					radios[name] = true;
					node = nodes.filter( '[name="' + name + '"]' );
				}
				// Let link by default refer to setting ID. If it doesn't exist, fallback to looking up by setting key.
				if ( node.data( 'customizeSettingLink' ) ) {
					setting = api( node.data( 'customizeSettingLink' ) );
				} else if ( node.data( 'customizeSettingKeyLink' ) ) {
					setting = control.settings[ node.data( 'customizeSettingKeyLink' ) ];
				}
				if ( setting ) {
					element = new api.Element( node );
					control.elements.push( element );
					element.sync( setting );
					element.set( setting() );
				}
			} );
		},
		/**
		 * Embed the control into the page.
		 */
		embed: function () {
			var control = this,
				inject;
			// Watch for changes to the section state.
			inject = function ( sectionId ) {
				var parentContainer;
				if ( ! sectionId ) { // @todo Allow a control to be embedded without a section, for instance a control embedded in the front end.
					return;
				}
				// Wait for the section to be registered.
				api.section( sectionId, function ( section ) {
					// Wait for the section to be ready/initialized.
					section.deferred.embedded.done( function () {
						parentContainer = ( section.contentContainer.is( 'ul' ) ) ? section.contentContainer : section.contentContainer.find( 'ul:first' );
						if ( ! control.container.parent().is( parentContainer ) ) {
							parentContainer.append( control.container );
						}
						control.renderContent();
						control.deferred.embedded.resolve();
					});
				});
			};
			control.section.bind( inject );
			inject( control.section.get() );
		},
		/**
		 * Triggered when the control's markup has been injected into the DOM.
		 *
		 * @return {void}
		 */
		ready: function() {
			var control = this, newItem;
			if ( 'dropdown-pages' === control.params.type && control.params.allow_addition ) {
				newItem = control.container.find( '.new-content-item-wrapper' );
				newItem.hide(); // Hide in JS to preserve flex display when showing.
				control.container.on( 'click', '.add-new-toggle', function( e ) {
					$( e.currentTarget ).slideUp( 180 );
					newItem.slideDown( 180 );
					newItem.find( '.create-item-input' ).focus();
				});
				control.container.on( 'click', '.add-content', function() {
					control.addNewPage();
				});
				control.container.on( 'keydown', '.create-item-input', function( e ) {
					if ( 13 === e.which ) { // Enter.
						control.addNewPage();
					}
				});
			}
		},
		/**
		 * Get the element inside of a control's container that contains the validation error message.
		 *
		 * Control subclasses may override this to return the proper container to render notifications into.
		 * Injects the notification container for existing controls that lack the necessary container,
		 * including special handling for nav menu items and widgets.
		 *
		 * @since 4.6.0
		 * @return {jQuery} Setting validation message element.
		 */
		getNotificationsContainerElement: function() {
			var control = this, controlTitle, notificationsContainer;
			notificationsContainer = control.container.find( '.customize-control-notifications-container:first' );
			if ( notificationsContainer.length ) {
				return notificationsContainer;
			}
			notificationsContainer = $( '' );
			if ( control.container.hasClass( 'customize-control-nav_menu_item' ) ) {
				control.container.find( '.menu-item-settings:first' ).prepend( notificationsContainer );
			} else if ( control.container.hasClass( 'customize-control-widget_form' ) ) {
				control.container.find( '.widget-inside:first' ).prepend( notificationsContainer );
			} else {
				controlTitle = control.container.find( '.customize-control-title' );
				if ( controlTitle.length ) {
					controlTitle.after( notificationsContainer );
				} else {
					control.container.prepend( notificationsContainer );
				}
			}
			return notificationsContainer;
		},
		/**
		 * Set up notifications.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		setupNotifications: function() {
			var control = this, renderNotificationsIfVisible, onSectionAssigned;
			// Add setting notifications to the control notification.
			_.each( control.settings, function( setting ) {
				if ( ! setting.notifications ) {
					return;
				}
				setting.notifications.bind( 'add', function( settingNotification ) {
					var params = _.extend(
						{},
						settingNotification,
						{
							setting: setting.id
						}
					);
					control.notifications.add( new api.Notification( setting.id + ':' + settingNotification.code, params ) );
				} );
				setting.notifications.bind( 'remove', function( settingNotification ) {
					control.notifications.remove( setting.id + ':' + settingNotification.code );
				} );
			} );
			renderNotificationsIfVisible = function() {
				var sectionId = control.section();
				if ( ! sectionId || ( api.section.has( sectionId ) && api.section( sectionId ).expanded() ) ) {
					control.notifications.render();
				}
			};
			control.notifications.bind( 'rendered', function() {
				var notifications = control.notifications.get();
				control.container.toggleClass( 'has-notifications', 0 !== notifications.length );
				control.container.toggleClass( 'has-error', 0 !== _.where( notifications, { type: 'error' } ).length );
			} );
			onSectionAssigned = function( newSectionId, oldSectionId ) {
				if ( oldSectionId && api.section.has( oldSectionId ) ) {
					api.section( oldSectionId ).expanded.unbind( renderNotificationsIfVisible );
				}
				if ( newSectionId ) {
					api.section( newSectionId, function( section ) {
						section.expanded.bind( renderNotificationsIfVisible );
						renderNotificationsIfVisible();
					});
				}
			};
			control.section.bind( onSectionAssigned );
			onSectionAssigned( control.section.get() );
			control.notifications.bind( 'change', _.debounce( renderNotificationsIfVisible ) );
		},
		/**
		 * Render notifications.
		 *
		 * Renders the `control.notifications` into the control's container.
		 * Control subclasses may override this method to do their own handling
		 * of rendering notifications.
		 *
		 * @deprecated in favor of `control.notifications.render()`
		 * @since 4.6.0
		 * @this {wp.customize.Control}
		 */
		renderNotifications: function() {
			var control = this, container, notifications, hasError = false;
			if ( 'undefined' !== typeof console && console.warn ) {
				console.warn( '[DEPRECATED] wp.customize.Control.prototype.renderNotifications() is deprecated in favor of instantiating a wp.customize.Notifications and calling its render() method.' );
			}
			container = control.getNotificationsContainerElement();
			if ( ! container || ! container.length ) {
				return;
			}
			notifications = [];
			control.notifications.each( function( notification ) {
				notifications.push( notification );
				if ( 'error' === notification.type ) {
					hasError = true;
				}
			} );
			if ( 0 === notifications.length ) {
				container.stop().slideUp( 'fast' );
			} else {
				container.stop().slideDown( 'fast', null, function() {
					$( this ).css( 'height', 'auto' );
				} );
			}
			if ( ! control.notificationsTemplate ) {
				control.notificationsTemplate = wp.template( 'customize-control-notifications' );
			}
			control.container.toggleClass( 'has-notifications', 0 !== notifications.length );
			control.container.toggleClass( 'has-error', hasError );
			container.empty().append(
				control.notificationsTemplate( { notifications: notifications, altNotice: Boolean( control.altNotice ) } ).trim()
			);
		},
		/**
		 * Normal controls do not expand, so just expand its parent
		 *
		 * @param {Object} [params]
		 */
		expand: function ( params ) {
			api.section( this.section() ).expand( params );
		},
		/*
		 * Documented using @borrows in the constructor.
		 */
		focus: focus,
		/**
		 * Update UI in response to a change in the control's active state.
		 * This does not change the active state, it merely handles the behavior
		 * for when it does change.
		 *
		 * @since 4.1.0
		 *
		 * @param {boolean}  active
		 * @param {Object}   args
		 * @param {number}   args.duration
		 * @param {Function} args.completeCallback
		 */
		onChangeActive: function ( active, args ) {
			if ( args.unchanged ) {
				if ( args.completeCallback ) {
					args.completeCallback();
				}
				return;
			}
			if ( ! $.contains( document, this.container[0] ) ) {
				// jQuery.fn.slideUp is not hiding an element if it is not in the DOM.
				this.container.toggle( active );
				if ( args.completeCallback ) {
					args.completeCallback();
				}
			} else if ( active ) {
				this.container.slideDown( args.duration, args.completeCallback );
			} else {
				this.container.slideUp( args.duration, args.completeCallback );
			}
		},
		/**
		 * @deprecated 4.1.0 Use this.onChangeActive() instead.
		 */
		toggle: function ( active ) {
			return this.onChangeActive( active, this.defaultActiveArguments );
		},
		/*
		 * Documented using @borrows in the constructor
		 */
		activate: Container.prototype.activate,
		/*
		 * Documented using @borrows in the constructor
		 */
		deactivate: Container.prototype.deactivate,
		/*
		 * Documented using @borrows in the constructor
		 */
		_toggleActive: Container.prototype._toggleActive,
		// @todo This function appears to be dead code and can be removed.
		dropdownInit: function() {
			var control      = this,
				statuses     = this.container.find('.dropdown-status'),
				params       = this.params,
				toggleFreeze = false,
				update       = function( to ) {
					if ( 'string' === typeof to && params.statuses && params.statuses[ to ] ) {
						statuses.html( params.statuses[ to ] ).show();
					} else {
						statuses.hide();
					}
				};
			// Support the .dropdown class to open/close complex elements.
			this.container.on( 'click keydown', '.dropdown', function( event ) {
				if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
					return;
				}
				event.preventDefault();
				if ( ! toggleFreeze ) {
					control.container.toggleClass( 'open' );
				}
				if ( control.container.hasClass( 'open' ) ) {
					control.container.parent().parent().find( 'li.library-selected' ).focus();
				}
				// Don't want to fire focus and click at same time.
				toggleFreeze = true;
				setTimeout(function () {
					toggleFreeze = false;
				}, 400);
			});
			this.setting.bind( update );
			update( this.setting() );
		},
		/**
		 * Render the control from its JS template, if it exists.
		 *
		 * The control's container must already exist in the DOM.
		 *
		 * @since 4.1.0
		 */
		renderContent: function () {
			var control = this, template, standardTypes, templateId, sectionId;
			standardTypes = [
				'button',
				'checkbox',
				'date',
				'datetime-local',
				'email',
				'month',
				'number',
				'password',
				'radio',
				'range',
				'search',
				'select',
				'tel',
				'time',
				'text',
				'textarea',
				'week',
				'url'
			];
			templateId = control.templateSelector;
			// Use default content template when a standard HTML type is used,
			// there isn't a more specific template existing, and the control container is empty.
			if ( templateId === 'customize-control-' + control.params.type + '-content' &&
				_.contains( standardTypes, control.params.type ) &&
				! document.getElementById( 'tmpl-' + templateId ) &&
				0 === control.container.children().length )
			{
				templateId = 'customize-control-default-content';
			}
			// Replace the container element's content with the control.
			if ( document.getElementById( 'tmpl-' + templateId ) ) {
				template = wp.template( templateId );
				if ( template && control.container ) {
					control.container.html( template( control.params ) );
				}
			}
			// Re-render notifications after content has been re-rendered.
			control.notifications.container = control.getNotificationsContainerElement();
			sectionId = control.section();
			if ( ! sectionId || ( api.section.has( sectionId ) && api.section( sectionId ).expanded() ) ) {
				control.notifications.render();
			}
		},
		/**
		 * Add a new page to a dropdown-pages control reusing menus code for this.
		 *
		 * @since 4.7.0
		 * @access private
		 *
		 * @return {void}
		 */
		addNewPage: function () {
			var control = this, promise, toggle, container, input, title, select;
			if ( 'dropdown-pages' !== control.params.type || ! control.params.allow_addition || ! api.Menus ) {
				return;
			}
			toggle = control.container.find( '.add-new-toggle' );
			container = control.container.find( '.new-content-item-wrapper' );
			input = control.container.find( '.create-item-input' );
			title = input.val();
			select = control.container.find( 'select' );
			if ( ! title ) {
				input.addClass( 'invalid' );
				return;
			}
			input.removeClass( 'invalid' );
			input.attr( 'disabled', 'disabled' );
			// The menus functions add the page, publish when appropriate,
			// and also add the new page to the dropdown-pages controls.
			promise = api.Menus.insertAutoDraftPost( {
				post_title: title,
				post_type: 'page'
			} );
			promise.done( function( data ) {
				var availableItem, $content, itemTemplate;
				// Prepare the new page as an available menu item.
				// See api.Menus.submitNew().
				availableItem = new api.Menus.AvailableItemModel( {
					'id': 'post-' + data.post_id, // Used for available menu item Backbone models.
					'title': title,
					'type': 'post_type',
					'type_label': api.Menus.data.l10n.page_label,
					'object': 'page',
					'object_id': data.post_id,
					'url': data.url
				} );
				// Add the new item to the list of available menu items.
				api.Menus.availableMenuItemsPanel.collection.add( availableItem );
				$content = $( '#available-menu-items-post_type-page' ).find( '.available-menu-items-list' );
				itemTemplate = wp.template( 'available-menu-item' );
				$content.prepend( itemTemplate( availableItem.attributes ) );
				// Focus the select control.
				select.focus();
				control.setting.set( String( data.post_id ) ); // Triggers a preview refresh and updates the setting.
				// Reset the create page form.
				container.slideUp( 180 );
				toggle.slideDown( 180 );
			} );
			promise.always( function() {
				input.val( '' ).removeAttr( 'disabled' );
			} );
		}
	});
	/**
	 * A colorpicker control.
	 *
	 * @class    wp.customize.ColorControl
	 * @augments wp.customize.Control
	 */
	api.ColorControl = api.Control.extend(/** @lends wp.customize.ColorControl.prototype */{
		ready: function() {
			var control = this,
				isHueSlider = this.params.mode === 'hue',
				updating = false,
				picker;
			if ( isHueSlider ) {
				picker = this.container.find( '.color-picker-hue' );
				picker.val( control.setting() ).wpColorPicker({
					change: function( event, ui ) {
						updating = true;
						control.setting( ui.color.h() );
						updating = false;
					}
				});
			} else {
				picker = this.container.find( '.color-picker-hex' );
				picker.val( control.setting() ).wpColorPicker({
					change: function() {
						updating = true;
						control.setting.set( picker.wpColorPicker( 'color' ) );
						updating = false;
					},
					clear: function() {
						updating = true;
						control.setting.set( '' );
						updating = false;
					}
				});
			}
			control.setting.bind( function ( value ) {
				// Bail if the update came from the control itself.
				if ( updating ) {
					return;
				}
				picker.val( value );
				picker.wpColorPicker( 'color', value );
			} );
			// Collapse color picker when hitting Esc instead of collapsing the current section.
			control.container.on( 'keydown', function( event ) {
				var pickerContainer;
				if ( 27 !== event.which ) { // Esc.
					return;
				}
				pickerContainer = control.container.find( '.wp-picker-container' );
				if ( pickerContainer.hasClass( 'wp-picker-active' ) ) {
					picker.wpColorPicker( 'close' );
					control.container.find( '.wp-color-result' ).focus();
					event.stopPropagation(); // Prevent section from being collapsed.
				}
			} );
		}
	});
	/**
	 * A control that implements the media modal.
	 *
	 * @class    wp.customize.MediaControl
	 * @augments wp.customize.Control
	 */
	api.MediaControl = api.Control.extend(/** @lends wp.customize.MediaControl.prototype */{
		/**
		 * When the control's DOM structure is ready,
		 * set up internal event bindings.
		 */
		ready: function() {
			var control = this;
			// Shortcut so that we don't have to use _.bind every time we add a callback.
			_.bindAll( control, 'restoreDefault', 'removeFile', 'openFrame', 'select', 'pausePlayer' );
			// Bind events, with delegation to facilitate re-rendering.
			control.container.on( 'click keydown', '.upload-button', control.openFrame );
			control.container.on( 'click keydown', '.upload-button', control.pausePlayer );
			control.container.on( 'click keydown', '.thumbnail-image img', control.openFrame );
			control.container.on( 'click keydown', '.default-button', control.restoreDefault );
			control.container.on( 'click keydown', '.remove-button', control.pausePlayer );
			control.container.on( 'click keydown', '.remove-button', control.removeFile );
			control.container.on( 'click keydown', '.remove-button', control.cleanupPlayer );
			// Resize the player controls when it becomes visible (ie when section is expanded).
			api.section( control.section() ).container
				.on( 'expanded', function() {
					if ( control.player ) {
						control.player.setControlsSize();
					}
				})
				.on( 'collapsed', function() {
					control.pausePlayer();
				});
			/**
			 * Set attachment data and render content.
			 *
			 * Note that BackgroundImage.prototype.ready applies this ready method
			 * to itself. Since BackgroundImage is an UploadControl, the value
			 * is the attachment URL instead of the attachment ID. In this case
			 * we skip fetching the attachment data because we have no ID available,
			 * and it is the responsibility of the UploadControl to set the control's
			 * attachmentData before calling the renderContent method.
			 *
			 * @param {number|string} value Attachment
			 */
			function setAttachmentDataAndRenderContent( value ) {
				var hasAttachmentData = $.Deferred();
				if ( control.extended( api.UploadControl ) ) {
					hasAttachmentData.resolve();
				} else {
					value = parseInt( value, 10 );
					if ( _.isNaN( value ) || value <= 0 ) {
						delete control.params.attachment;
						hasAttachmentData.resolve();
					} else if ( control.params.attachment && control.params.attachment.id === value ) {
						hasAttachmentData.resolve();
					}
				}
				// Fetch the attachment data.
				if ( 'pending' === hasAttachmentData.state() ) {
					wp.media.attachment( value ).fetch().done( function() {
						control.params.attachment = this.attributes;
						hasAttachmentData.resolve();
						// Send attachment information to the preview for possible use in `postMessage` transport.
						wp.customize.previewer.send( control.setting.id + '-attachment-data', this.attributes );
					} );
				}
				hasAttachmentData.done( function() {
					control.renderContent();
				} );
			}
			// Ensure attachment data is initially set (for dynamically-instantiated controls).
			setAttachmentDataAndRenderContent( control.setting() );
			// Update the attachment data and re-render the control when the setting changes.
			control.setting.bind( setAttachmentDataAndRenderContent );
		},
		pausePlayer: function () {
			this.player && this.player.pause();
		},
		cleanupPlayer: function () {
			this.player && wp.media.mixin.removePlayer( this.player );
		},
		/**
		 * Open the media modal.
		 */
		openFrame: function( event ) {
			if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
				return;
			}
			event.preventDefault();
			if ( ! this.frame ) {
				this.initFrame();
			}
			this.frame.open();
		},
		/**
		 * Create a media modal select frame, and store it so the instance can be reused when needed.
		 */
		initFrame: function() {
			this.frame = wp.media({
				button: {
					text: this.params.button_labels.frame_button
				},
				states: [
					new wp.media.controller.Library({
						title:     this.params.button_labels.frame_title,
						library:   wp.media.query({ type: this.params.mime_type }),
						multiple:  false,
						date:      false
					})
				]
			});
			// When a file is selected, run a callback.
			this.frame.on( 'select', this.select );
		},
		/**
		 * Callback handler for when an attachment is selected in the media modal.
		 * Gets the selected image information, and sets it within the control.
		 */
		select: function() {
			// Get the attachment from the modal frame.
			var node,
				attachment = this.frame.state().get( 'selection' ).first().toJSON(),
				mejsSettings = window._wpmejsSettings || {};
			this.params.attachment = attachment;
			// Set the Customizer setting; the callback takes care of rendering.
			this.setting( attachment.id );
			node = this.container.find( 'audio, video' ).get(0);
			// Initialize audio/video previews.
			if ( node ) {
				this.player = new MediaElementPlayer( node, mejsSettings );
			} else {
				this.cleanupPlayer();
			}
		},
		/**
		 * Reset the setting to the default value.
		 */
		restoreDefault: function( event ) {
			if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
				return;
			}
			event.preventDefault();
			this.params.attachment = this.params.defaultAttachment;
			this.setting( this.params.defaultAttachment.url );
		},
		/**
		 * Called when the "Remove" link is clicked. Empties the setting.
		 *
		 * @param {Object} event jQuery Event object
		 */
		removeFile: function( event ) {
			if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
				return;
			}
			event.preventDefault();
			this.params.attachment = {};
			this.setting( '' );
			this.renderContent(); // Not bound to setting change when emptying.
		}
	});
	/**
	 * An upload control, which utilizes the media modal.
	 *
	 * @class    wp.customize.UploadControl
	 * @augments wp.customize.MediaControl
	 */
	api.UploadControl = api.MediaControl.extend(/** @lends wp.customize.UploadControl.prototype */{
		/**
		 * Callback handler for when an attachment is selected in the media modal.
		 * Gets the selected image information, and sets it within the control.
		 */
		select: function() {
			// Get the attachment from the modal frame.
			var node,
				attachment = this.frame.state().get( 'selection' ).first().toJSON(),
				mejsSettings = window._wpmejsSettings || {};
			this.params.attachment = attachment;
			// Set the Customizer setting; the callback takes care of rendering.
			this.setting( attachment.url );
			node = this.container.find( 'audio, video' ).get(0);
			// Initialize audio/video previews.
			if ( node ) {
				this.player = new MediaElementPlayer( node, mejsSettings );
			} else {
				this.cleanupPlayer();
			}
		},
		// @deprecated
		success: function() {},
		// @deprecated
		removerVisibility: function() {}
	});
	/**
	 * A control for uploading images.
	 *
	 * This control no longer needs to do anything more
	 * than what the upload control does in JS.
	 *
	 * @class    wp.customize.ImageControl
	 * @augments wp.customize.UploadControl
	 */
	api.ImageControl = api.UploadControl.extend(/** @lends wp.customize.ImageControl.prototype */{
		// @deprecated
		thumbnailSrc: function() {}
	});
	/**
	 * A control for uploading background images.
	 *
	 * @class    wp.customize.BackgroundControl
	 * @augments wp.customize.UploadControl
	 */
	api.BackgroundControl = api.UploadControl.extend(/** @lends wp.customize.BackgroundControl.prototype */{
		/**
		 * When the control's DOM structure is ready,
		 * set up internal event bindings.
		 */
		ready: function() {
			api.UploadControl.prototype.ready.apply( this, arguments );
		},
		/**
		 * Callback handler for when an attachment is selected in the media modal.
		 * Does an additional Ajax request for setting the background context.
		 */
		select: function() {
			api.UploadControl.prototype.select.apply( this, arguments );
			wp.ajax.post( 'custom-background-add', {
				nonce: _wpCustomizeBackground.nonces.add,
				wp_customize: 'on',
				customize_theme: api.settings.theme.stylesheet,
				attachment_id: this.params.attachment.id
			} );
		}
	});
	/**
	 * A control for positioning a background image.
	 *
	 * @since 4.7.0
	 *
	 * @class    wp.customize.BackgroundPositionControl
	 * @augments wp.customize.Control
	 */
	api.BackgroundPositionControl = api.Control.extend(/** @lends wp.customize.BackgroundPositionControl.prototype */{
		/**
		 * Set up control UI once embedded in DOM and settings are created.
		 *
		 * @since 4.7.0
		 * @access public
		 */
		ready: function() {
			var control = this, updateRadios;
			control.container.on( 'change', 'input[name="background-position"]', function() {
				var position = $( this ).val().split( ' ' );
				control.settings.x( position[0] );
				control.settings.y( position[1] );
			} );
			updateRadios = _.debounce( function() {
				var x, y, radioInput, inputValue;
				x = control.settings.x.get();
				y = control.settings.y.get();
				inputValue = String( x ) + ' ' + String( y );
				radioInput = control.container.find( 'input[name="background-position"][value="' + inputValue + '"]' );
				radioInput.trigger( 'click' );
			} );
			control.settings.x.bind( updateRadios );
			control.settings.y.bind( updateRadios );
			updateRadios(); // Set initial UI.
		}
	} );
	/**
	 * A control for selecting and cropping an image.
	 *
	 * @class    wp.customize.CroppedImageControl
	 * @augments wp.customize.MediaControl
	 */
	api.CroppedImageControl = api.MediaControl.extend(/** @lends wp.customize.CroppedImageControl.prototype */{
		/**
		 * Open the media modal to the library state.
		 */
		openFrame: function( event ) {
			if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
				return;
			}
			this.initFrame();
			this.frame.setState( 'library' ).open();
		},
		/**
		 * Create a media modal select frame, and store it so the instance can be reused when needed.
		 */
		initFrame: function() {
			var l10n = _wpMediaViewsL10n;
			this.frame = wp.media({
				button: {
					text: l10n.select,
					close: false
				},
				states: [
					new wp.media.controller.Library({
						title: this.params.button_labels.frame_title,
						library: wp.media.query({ type: 'image' }),
						multiple: false,
						date: false,
						priority: 20,
						suggestedWidth: this.params.width,
						suggestedHeight: this.params.height
					}),
					new wp.media.controller.CustomizeImageCropper({
						imgSelectOptions: this.calculateImageSelectOptions,
						control: this
					})
				]
			});
			this.frame.on( 'select', this.onSelect, this );
			this.frame.on( 'cropped', this.onCropped, this );
			this.frame.on( 'skippedcrop', this.onSkippedCrop, this );
		},
		/**
		 * After an image is selected in the media modal, switch to the cropper
		 * state if the image isn't the right size.
		 */
		onSelect: function() {
			var attachment = this.frame.state().get( 'selection' ).first().toJSON();
			if ( this.params.width === attachment.width && this.params.height === attachment.height && ! this.params.flex_width && ! this.params.flex_height ) {
				this.setImageFromAttachment( attachment );
				this.frame.close();
			} else {
				this.frame.setState( 'cropper' );
			}
		},
		/**
		 * After the image has been cropped, apply the cropped image data to the setting.
		 *
		 * @param {Object} croppedImage Cropped attachment data.
		 */
		onCropped: function( croppedImage ) {
			this.setImageFromAttachment( croppedImage );
		},
		/**
		 * Returns a set of options, computed from the attached image data and
		 * control-specific data, to be fed to the imgAreaSelect plugin in
		 * wp.media.view.Cropper.
		 *
		 * @param {wp.media.model.Attachment} attachment
		 * @param {wp.media.controller.Cropper} controller
		 * @return {Object} Options
		 */
		calculateImageSelectOptions: function( attachment, controller ) {
			var control       = controller.get( 'control' ),
				flexWidth     = !! parseInt( control.params.flex_width, 10 ),
				flexHeight    = !! parseInt( control.params.flex_height, 10 ),
				realWidth     = attachment.get( 'width' ),
				realHeight    = attachment.get( 'height' ),
				xInit         = parseInt( control.params.width, 10 ),
				yInit         = parseInt( control.params.height, 10 ),
				requiredRatio = xInit / yInit,
				realRatio     = realWidth / realHeight,
				xImg          = xInit,
				yImg          = yInit,
				x1, y1, imgSelectOptions;
			controller.set( 'hasRequiredAspectRatio', control.hasRequiredAspectRatio( requiredRatio, realRatio ) );
			controller.set( 'suggestedCropSize', { width: realWidth, height: realHeight, x1: 0, y1: 0, x2: xInit, y2: yInit } );
			controller.set( 'canSkipCrop', ! control.mustBeCropped( flexWidth, flexHeight, xInit, yInit, realWidth, realHeight ) );
			if ( realRatio > requiredRatio ) {
				yInit = realHeight;
				xInit = yInit * requiredRatio;
			} else {
				xInit = realWidth;
				yInit = xInit / requiredRatio;
			}
			x1 = ( realWidth - xInit ) / 2;
			y1 = ( realHeight - yInit ) / 2;
			imgSelectOptions = {
				handles: true,
				keys: true,
				instance: true,
				persistent: true,
				imageWidth: realWidth,
				imageHeight: realHeight,
				minWidth: xImg > xInit ? xInit : xImg,
				minHeight: yImg > yInit ? yInit : yImg,
				x1: x1,
				y1: y1,
				x2: xInit + x1,
				y2: yInit + y1
			};
			if ( flexHeight === false && flexWidth === false ) {
				imgSelectOptions.aspectRatio = xInit + ':' + yInit;
			}
			if ( true === flexHeight ) {
				delete imgSelectOptions.minHeight;
				imgSelectOptions.maxWidth = realWidth;
			}
			if ( true === flexWidth ) {
				delete imgSelectOptions.minWidth;
				imgSelectOptions.maxHeight = realHeight;
			}
			return imgSelectOptions;
		},
		/**
		 * Return whether the image must be cropped, based on required dimensions.
		 *
		 * @param {boolean} flexW Width is flexible.
		 * @param {boolean} flexH Height is flexible.
		 * @param {number}  dstW  Required width.
		 * @param {number}  dstH  Required height.
		 * @param {number}  imgW  Provided image's width.
		 * @param {number}  imgH  Provided image's height.
		 * @return {boolean} Whether cropping is required.
		 */
		mustBeCropped: function( flexW, flexH, dstW, dstH, imgW, imgH ) {
			if ( true === flexW && true === flexH ) {
				return false;
			}
			if ( true === flexW && dstH === imgH ) {
				return false;
			}
			if ( true === flexH && dstW === imgW ) {
				return false;
			}
			if ( dstW === imgW && dstH === imgH ) {
				return false;
			}
			if ( imgW <= dstW ) {
				return false;
			}
			return true;
		},
		/**
		 * Check if the image's aspect ratio essentially matches the required aspect ratio.
		 *
		 * Floating point precision is low, so this allows a small tolerance. This
		 * tolerance allows for images over 100,000 px on either side to still trigger
		 * the cropping flow.
		 *
		 * @param {number} requiredRatio Required image ratio.
		 * @param {number} realRatio     Provided image ratio.
		 * @return {boolean} Whether the image has the required aspect ratio.
		 */
		hasRequiredAspectRatio: function ( requiredRatio, realRatio ) {
			if ( Math.abs( requiredRatio - realRatio ) < 0.000001 ) {
				return true;
			}
			return false;
		},
		/**
		 * If cropping was skipped, apply the image data directly to the setting.
		 */
		onSkippedCrop: function() {
			var attachment = this.frame.state().get( 'selection' ).first().toJSON();
			this.setImageFromAttachment( attachment );
		},
		/**
		 * Updates the setting and re-renders the control UI.
		 *
		 * @param {Object} attachment
		 */
		setImageFromAttachment: function( attachment ) {
			this.params.attachment = attachment;
			// Set the Customizer setting; the callback takes care of rendering.
			this.setting( attachment.id );
		}
	});
	/**
	 * A control for selecting and cropping Site Icons.
	 *
	 * @class    wp.customize.SiteIconControl
	 * @augments wp.customize.CroppedImageControl
	 */
	api.SiteIconControl = api.CroppedImageControl.extend(/** @lends wp.customize.SiteIconControl.prototype */{
		/**
		 * Create a media modal select frame, and store it so the instance can be reused when needed.
		 */
		initFrame: function() {
			var l10n = _wpMediaViewsL10n;
			this.frame = wp.media({
				button: {
					text: l10n.select,
					close: false
				},
				states: [
					new wp.media.controller.Library({
						title: this.params.button_labels.frame_title,
						library: wp.media.query({ type: 'image' }),
						multiple: false,
						date: false,
						priority: 20,
						suggestedWidth: this.params.width,
						suggestedHeight: this.params.height
					}),
					new wp.media.controller.SiteIconCropper({
						imgSelectOptions: this.calculateImageSelectOptions,
						control: this
					})
				]
			});
			this.frame.on( 'select', this.onSelect, this );
			this.frame.on( 'cropped', this.onCropped, this );
			this.frame.on( 'skippedcrop', this.onSkippedCrop, this );
		},
		/**
		 * After an image is selected in the media modal, switch to the cropper
		 * state if the image isn't the right size.
		 */
		onSelect: function() {
			var attachment = this.frame.state().get( 'selection' ).first().toJSON(),
				controller = this;
			if ( this.params.width === attachment.width && this.params.height === attachment.height && ! this.params.flex_width && ! this.params.flex_height ) {
				wp.ajax.post( 'crop-image', {
					nonce: attachment.nonces.edit,
					id: attachment.id,
					context: 'site-icon',
					cropDetails: {
						x1: 0,
						y1: 0,
						width: this.params.width,
						height: this.params.height,
						dst_width: this.params.width,
						dst_height: this.params.height
					}
				} ).done( function( croppedImage ) {
					controller.setImageFromAttachment( croppedImage );
					controller.frame.close();
				} ).fail( function() {
					controller.frame.trigger('content:error:crop');
				} );
			} else {
				this.frame.setState( 'cropper' );
			}
		},
		/**
		 * Updates the setting and re-renders the control UI.
		 *
		 * @param {Object} attachment
		 */
		setImageFromAttachment: function( attachment ) {
			var sizes = [ 'site_icon-32', 'thumbnail', 'full' ], link,
				icon;
			_.each( sizes, function( size ) {
				if ( ! icon && ! _.isUndefined ( attachment.sizes[ size ] ) ) {
					icon = attachment.sizes[ size ];
				}
			} );
			this.params.attachment = attachment;
			// Set the Customizer setting; the callback takes care of rendering.
			this.setting( attachment.id );
			if ( ! icon ) {
				return;
			}
			// Update the icon in-browser.
			link = $( 'link[rel="icon"][sizes="32x32"]' );
			link.attr( 'href', icon.url );
		},
		/**
		 * Called when the "Remove" link is clicked. Empties the setting.
		 *
		 * @param {Object} event jQuery Event object
		 */
		removeFile: function( event ) {
			if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
				return;
			}
			event.preventDefault();
			this.params.attachment = {};
			this.setting( '' );
			this.renderContent(); // Not bound to setting change when emptying.
			$( 'link[rel="icon"][sizes="32x32"]' ).attr( 'href', '/favicon.ico' ); // Set to default.
		}
	});
	/**
	 * @class    wp.customize.HeaderControl
	 * @augments wp.customize.Control
	 */
	api.HeaderControl = api.Control.extend(/** @lends wp.customize.HeaderControl.prototype */{
		ready: function() {
			this.btnRemove = $('#customize-control-header_image .actions .remove');
			this.btnNew    = $('#customize-control-header_image .actions .new');
			_.bindAll(this, 'openMedia', 'removeImage');
			this.btnNew.on( 'click', this.openMedia );
			this.btnRemove.on( 'click', this.removeImage );
			api.HeaderTool.currentHeader = this.getInitialHeaderImage();
			new api.HeaderTool.CurrentView({
				model: api.HeaderTool.currentHeader,
				el: '#customize-control-header_image .current .container'
			});
			new api.HeaderTool.ChoiceListView({
				collection: api.HeaderTool.UploadsList = new api.HeaderTool.ChoiceList(),
				el: '#customize-control-header_image .choices .uploaded .list'
			});
			new api.HeaderTool.ChoiceListView({
				collection: api.HeaderTool.DefaultsList = new api.HeaderTool.DefaultsList(),
				el: '#customize-control-header_image .choices .default .list'
			});
			api.HeaderTool.combinedList = api.HeaderTool.CombinedList = new api.HeaderTool.CombinedList([
				api.HeaderTool.UploadsList,
				api.HeaderTool.DefaultsList
			]);
			// Ensure custom-header-crop Ajax requests bootstrap the Customizer to activate the previewed theme.
			wp.media.controller.Cropper.prototype.defaults.doCropArgs.wp_customize = 'on';
			wp.media.controller.Cropper.prototype.defaults.doCropArgs.customize_theme = api.settings.theme.stylesheet;
		},
		/**
		 * Returns a new instance of api.HeaderTool.ImageModel based on the currently
		 * saved header image (if any).
		 *
		 * @since 4.2.0
		 *
		 * @return {Object} Options
		 */
		getInitialHeaderImage: function() {
			if ( ! api.get().header_image || ! api.get().header_image_data || _.contains( [ 'remove-header', 'random-default-image', 'random-uploaded-image' ], api.get().header_image ) ) {
				return new api.HeaderTool.ImageModel();
			}
			// Get the matching uploaded image object.
			var currentHeaderObject = _.find( _wpCustomizeHeader.uploads, function( imageObj ) {
				return ( imageObj.attachment_id === api.get().header_image_data.attachment_id );
			} );
			// Fall back to raw current header image.
			if ( ! currentHeaderObject ) {
				currentHeaderObject = {
					url: api.get().header_image,
					thumbnail_url: api.get().header_image,
					attachment_id: api.get().header_image_data.attachment_id
				};
			}
			return new api.HeaderTool.ImageModel({
				header: currentHeaderObject,
				choice: currentHeaderObject.url.split( '/' ).pop()
			});
		},
		/**
		 * Returns a set of options, computed from the attached image data and
		 * theme-specific data, to be fed to the imgAreaSelect plugin in
		 * wp.media.view.Cropper.
		 *
		 * @param {wp.media.model.Attachment} attachment
		 * @param {wp.media.controller.Cropper} controller
		 * @return {Object} Options
		 */
		calculateImageSelectOptions: function(attachment, controller) {
			var xInit = parseInt(_wpCustomizeHeader.data.width, 10),
				yInit = parseInt(_wpCustomizeHeader.data.height, 10),
				flexWidth = !! parseInt(_wpCustomizeHeader.data['flex-width'], 10),
				flexHeight = !! parseInt(_wpCustomizeHeader.data['flex-height'], 10),
				ratio, xImg, yImg, realHeight, realWidth,
				imgSelectOptions;
			realWidth = attachment.get('width');
			realHeight = attachment.get('height');
			this.headerImage = new api.HeaderTool.ImageModel();
			this.headerImage.set({
				themeWidth: xInit,
				themeHeight: yInit,
				themeFlexWidth: flexWidth,
				themeFlexHeight: flexHeight,
				imageWidth: realWidth,
				imageHeight: realHeight
			});
			controller.set( 'canSkipCrop', ! this.headerImage.shouldBeCropped() );
			ratio = xInit / yInit;
			xImg = realWidth;
			yImg = realHeight;
			if ( xImg / yImg > ratio ) {
				yInit = yImg;
				xInit = yInit * ratio;
			} else {
				xInit = xImg;
				yInit = xInit / ratio;
			}
			imgSelectOptions = {
				handles: true,
				keys: true,
				instance: true,
				persistent: true,
				imageWidth: realWidth,
				imageHeight: realHeight,
				x1: 0,
				y1: 0,
				x2: xInit,
				y2: yInit
			};
			if (flexHeight === false && flexWidth === false) {
				imgSelectOptions.aspectRatio = xInit + ':' + yInit;
			}
			if (flexHeight === false ) {
				imgSelectOptions.maxHeight = yInit;
			}
			if (flexWidth === false ) {
				imgSelectOptions.maxWidth = xInit;
			}
			return imgSelectOptions;
		},
		/**
		 * Sets up and opens the Media Manager in order to select an image.
		 * Depending on both the size of the image and the properties of the
		 * current theme, a cropping step after selection may be required or
		 * skippable.
		 *
		 * @param {event} event
		 */
		openMedia: function(event) {
			var l10n = _wpMediaViewsL10n;
			event.preventDefault();
			this.frame = wp.media({
				button: {
					text: l10n.selectAndCrop,
					close: false
				},
				states: [
					new wp.media.controller.Library({
						title:     l10n.chooseImage,
						library:   wp.media.query({ type: 'image' }),
						multiple:  false,
						date:      false,
						priority:  20,
						suggestedWidth: _wpCustomizeHeader.data.width,
						suggestedHeight: _wpCustomizeHeader.data.height
					}),
					new wp.media.controller.Cropper({
						imgSelectOptions: this.calculateImageSelectOptions
					})
				]
			});
			this.frame.on('select', this.onSelect, this);
			this.frame.on('cropped', this.onCropped, this);
			this.frame.on('skippedcrop', this.onSkippedCrop, this);
			this.frame.open();
		},
		/**
		 * After an image is selected in the media modal,
		 * switch to the cropper state.
		 */
		onSelect: function() {
			this.frame.setState('cropper');
		},
		/**
		 * After the image has been cropped, apply the cropped image data to the setting.
		 *
		 * @param {Object} croppedImage Cropped attachment data.
		 */
		onCropped: function(croppedImage) {
			var url = croppedImage.url,
				attachmentId = croppedImage.attachment_id,
				w = croppedImage.width,
				h = croppedImage.height;
			this.setImageFromURL(url, attachmentId, w, h);
		},
		/**
		 * If cropping was skipped, apply the image data directly to the setting.
		 *
		 * @param {Object} selection
		 */
		onSkippedCrop: function(selection) {
			var url = selection.get('url'),
				w = selection.get('width'),
				h = selection.get('height');
			this.setImageFromURL(url, selection.id, w, h);
		},
		/**
		 * Creates a new wp.customize.HeaderTool.ImageModel from provided
		 * header image data and inserts it into the user-uploaded headers
		 * collection.
		 *
		 * @param {string} url
		 * @param {number} attachmentId
		 * @param {number} width
		 * @param {number} height
		 */
		setImageFromURL: function(url, attachmentId, width, height) {
			var choice, data = {};
			data.url = url;
			data.thumbnail_url = url;
			data.timestamp = _.now();
			if (attachmentId) {
				data.attachment_id = attachmentId;
			}
			if (width) {
				data.width = width;
			}
			if (height) {
				data.height = height;
			}
			choice = new api.HeaderTool.ImageModel({
				header: data,
				choice: url.split('/').pop()
			});
			api.HeaderTool.UploadsList.add(choice);
			api.HeaderTool.currentHeader.set(choice.toJSON());
			choice.save();
			choice.importImage();
		},
		/**
		 * Triggers the necessary events to deselect an image which was set as
		 * the currently selected one.
		 */
		removeImage: function() {
			api.HeaderTool.currentHeader.trigger('hide');
			api.HeaderTool.CombinedList.trigger('control:removeImage');
		}
	});
	/**
	 * wp.customize.ThemeControl
	 *
	 * @class    wp.customize.ThemeControl
	 * @augments wp.customize.Control
	 */
	api.ThemeControl = api.Control.extend(/** @lends wp.customize.ThemeControl.prototype */{
		touchDrag: false,
		screenshotRendered: false,
		/**
		 * @since 4.2.0
		 */
		ready: function() {
			var control = this, panel = api.panel( 'themes' );
			function disableSwitchButtons() {
				return ! panel.canSwitchTheme( control.params.theme.id );
			}
			// Temporary special function since supplying SFTP credentials does not work yet. See #42184.
			function disableInstallButtons() {
				return disableSwitchButtons() || false === api.settings.theme._canInstall || true === api.settings.theme._filesystemCredentialsNeeded;
			}
			function updateButtons() {
				control.container.find( 'button.preview, button.preview-theme' ).toggleClass( 'disabled', disableSwitchButtons() );
				control.container.find( 'button.theme-install' ).toggleClass( 'disabled', disableInstallButtons() );
			}
			api.state( 'selectedChangesetStatus' ).bind( updateButtons );
			api.state( 'changesetStatus' ).bind( updateButtons );
			updateButtons();
			control.container.on( 'touchmove', '.theme', function() {
				control.touchDrag = true;
			});
			// Bind details view trigger.
			control.container.on( 'click keydown touchend', '.theme', function( event ) {
				var section;
				if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
					return;
				}
				// Bail if the user scrolled on a touch device.
				if ( control.touchDrag === true ) {
					return control.touchDrag = false;
				}
				// Prevent the modal from showing when the user clicks the action button.
				if ( $( event.target ).is( '.theme-actions .button, .update-theme' ) ) {
					return;
				}
				event.preventDefault(); // Keep this AFTER the key filter above.
				section = api.section( control.section() );
				section.showDetails( control.params.theme, function() {
					// Temporary special function since supplying SFTP credentials does not work yet. See #42184.
					if ( api.settings.theme._filesystemCredentialsNeeded ) {
						section.overlay.find( '.theme-actions .delete-theme' ).remove();
					}
				} );
			});
			control.container.on( 'render-screenshot', function() {
				var $screenshot = $( this ).find( 'img' ),
					source = $screenshot.data( 'src' );
				if ( source ) {
					$screenshot.attr( 'src', source );
				}
				control.screenshotRendered = true;
			});
		},
		/**
		 * Show or hide the theme based on the presence of the term in the title, description, tags, and author.
		 *
		 * @since 4.2.0
		 * @param {Array} terms - An array of terms to search for.
		 * @return {boolean} Whether a theme control was activated or not.
		 */
		filter: function( terms ) {
			var control = this,
				matchCount = 0,
				haystack = control.params.theme.name + ' ' +
					control.params.theme.description + ' ' +
					control.params.theme.tags + ' ' +
					control.params.theme.author + ' ';
			haystack = haystack.toLowerCase().replace( '-', ' ' );
			// Back-compat for behavior in WordPress 4.2.0 to 4.8.X.
			if ( ! _.isArray( terms ) ) {
				terms = [ terms ];
			}
			// Always give exact name matches highest ranking.
			if ( control.params.theme.name.toLowerCase() === terms.join( ' ' ) ) {
				matchCount = 100;
			} else {
				// Search for and weight (by 10) complete term matches.
				matchCount = matchCount + 10 * ( haystack.split( terms.join( ' ' ) ).length - 1 );
				// Search for each term individually (as whole-word and partial match) and sum weighted match counts.
				_.each( terms, function( term ) {
					matchCount = matchCount + 2 * ( haystack.split( term + ' ' ).length - 1 ); // Whole-word, double-weighted.
					matchCount = matchCount + haystack.split( term ).length - 1; // Partial word, to minimize empty intermediate searches while typing.
				});
				// Upper limit on match ranking.
				if ( matchCount > 99 ) {
					matchCount = 99;
				}
			}
			if ( 0 !== matchCount ) {
				control.activate();
				control.params.priority = 101 - matchCount; // Sort results by match count.
				return true;
			} else {
				control.deactivate(); // Hide control.
				control.params.priority = 101;
				return false;
			}
		},
		/**
		 * Rerender the theme from its JS template with the installed type.
		 *
		 * @since 4.9.0
		 *
		 * @return {void}
		 */
		rerenderAsInstalled: function( installed ) {
			var control = this, section;
			if ( installed ) {
				control.params.theme.type = 'installed';
			} else {
				section = api.section( control.params.section );
				control.params.theme.type = section.params.action;
			}
			control.renderContent(); // Replaces existing content.
			control.container.trigger( 'render-screenshot' );
		}
	});
	/**
	 * Class wp.customize.CodeEditorControl
	 *
	 * @since 4.9.0
	 *
	 * @class    wp.customize.CodeEditorControl
	 * @augments wp.customize.Control
	 */
	api.CodeEditorControl = api.Control.extend(/** @lends wp.customize.CodeEditorControl.prototype */{
		/**
		 * Initialize.
		 *
		 * @since 4.9.0
		 * @param {string} id      - Unique identifier for the control instance.
		 * @param {Object} options - Options hash for the control instance.
		 * @return {void}
		 */
		initialize: function( id, options ) {
			var control = this;
			control.deferred = _.extend( control.deferred || {}, {
				codemirror: $.Deferred()
			} );
			api.Control.prototype.initialize.call( control, id, options );
			// Note that rendering is debounced so the props will be used when rendering happens after add event.
			control.notifications.bind( 'add', function( notification ) {
				// Skip if control notification is not from setting csslint_error notification.
				if ( notification.code !== control.setting.id + ':csslint_error' ) {
					return;
				}
				// Customize the template and behavior of csslint_error notifications.
				notification.templateId = 'customize-code-editor-lint-error-notification';
				notification.render = (function( render ) {
					return function() {
						var li = render.call( this );
						li.find( 'input[type=checkbox]' ).on( 'click', function() {
							control.setting.notifications.remove( 'csslint_error' );
						} );
						return li;
					};
				})( notification.render );
			} );
		},
		/**
		 * Initialize the editor when the containing section is ready and expanded.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		ready: function() {
			var control = this;
			if ( ! control.section() ) {
				control.initEditor();
				return;
			}
			// Wait to initialize editor until section is embedded and expanded.
			api.section( control.section(), function( section ) {
				section.deferred.embedded.done( function() {
					var onceExpanded;
					if ( section.expanded() ) {
						control.initEditor();
					} else {
						onceExpanded = function( isExpanded ) {
							if ( isExpanded ) {
								control.initEditor();
								section.expanded.unbind( onceExpanded );
							}
						};
						section.expanded.bind( onceExpanded );
					}
				} );
			} );
		},
		/**
		 * Initialize editor.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		initEditor: function() {
			var control = this, element, editorSettings = false;
			// Obtain editorSettings for instantiation.
			if ( wp.codeEditor && ( _.isUndefined( control.params.editor_settings ) || false !== control.params.editor_settings ) ) {
				// Obtain default editor settings.
				editorSettings = wp.codeEditor.defaultSettings ? _.clone( wp.codeEditor.defaultSettings ) : {};
				editorSettings.codemirror = _.extend(
					{},
					editorSettings.codemirror,
					{
						indentUnit: 2,
						tabSize: 2
					}
				);
				// Merge editor_settings param on top of defaults.
				if ( _.isObject( control.params.editor_settings ) ) {
					_.each( control.params.editor_settings, function( value, key ) {
						if ( _.isObject( value ) ) {
							editorSettings[ key ] = _.extend(
								{},
								editorSettings[ key ],
								value
							);
						}
					} );
				}
			}
			element = new api.Element( control.container.find( 'textarea' ) );
			control.elements.push( element );
			element.sync( control.setting );
			element.set( control.setting() );
			if ( editorSettings ) {
				control.initSyntaxHighlightingEditor( editorSettings );
			} else {
				control.initPlainTextareaEditor();
			}
		},
		/**
		 * Make sure editor gets focused when control is focused.
		 *
		 * @since 4.9.0
		 * @param {Object}   [params] - Focus params.
		 * @param {Function} [params.completeCallback] - Function to call when expansion is complete.
		 * @return {void}
		 */
		focus: function( params ) {
			var control = this, extendedParams = _.extend( {}, params ), originalCompleteCallback;
			originalCompleteCallback = extendedParams.completeCallback;
			extendedParams.completeCallback = function() {
				if ( originalCompleteCallback ) {
					originalCompleteCallback();
				}
				if ( control.editor ) {
					control.editor.codemirror.focus();
				}
			};
			api.Control.prototype.focus.call( control, extendedParams );
		},
		/**
		 * Initialize syntax-highlighting editor.
		 *
		 * @since 4.9.0
		 * @param {Object} codeEditorSettings - Code editor settings.
		 * @return {void}
		 */
		initSyntaxHighlightingEditor: function( codeEditorSettings ) {
			var control = this, $textarea = control.container.find( 'textarea' ), settings, suspendEditorUpdate = false;
			settings = _.extend( {}, codeEditorSettings, {
				onTabNext: _.bind( control.onTabNext, control ),
				onTabPrevious: _.bind( control.onTabPrevious, control ),
				onUpdateErrorNotice: _.bind( control.onUpdateErrorNotice, control )
			});
			control.editor = wp.codeEditor.initialize( $textarea, settings );
			// Improve the editor accessibility.
			$( control.editor.codemirror.display.lineDiv )
				.attr({
					role: 'textbox',
					'aria-multiline': 'true',
					'aria-label': control.params.label,
					'aria-describedby': 'editor-keyboard-trap-help-1 editor-keyboard-trap-help-2 editor-keyboard-trap-help-3 editor-keyboard-trap-help-4'
				});
			// Focus the editor when clicking on its label.
			control.container.find( 'label' ).on( 'click', function() {
				control.editor.codemirror.focus();
			});
			/*
			 * When the CodeMirror instance changes, mirror to the textarea,
			 * where we have our "true" change event handler bound.
			 */
			control.editor.codemirror.on( 'change', function( codemirror ) {
				suspendEditorUpdate = true;
				$textarea.val( codemirror.getValue() ).trigger( 'change' );
				suspendEditorUpdate = false;
			});
			// Update CodeMirror when the setting is changed by another plugin.
			control.setting.bind( function( value ) {
				if ( ! suspendEditorUpdate ) {
					control.editor.codemirror.setValue( value );
				}
			});
			// Prevent collapsing section when hitting Esc to tab out of editor.
			control.editor.codemirror.on( 'keydown', function onKeydown( codemirror, event ) {
				var escKeyCode = 27;
				if ( escKeyCode === event.keyCode ) {
					event.stopPropagation();
				}
			});
			control.deferred.codemirror.resolveWith( control, [ control.editor.codemirror ] );
		},
		/**
		 * Handle tabbing to the field after the editor.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		onTabNext: function onTabNext() {
			var control = this, controls, controlIndex, section;
			section = api.section( control.section() );
			controls = section.controls();
			controlIndex = controls.indexOf( control );
			if ( controls.length === controlIndex + 1 ) {
				$( '#customize-footer-actions .collapse-sidebar' ).trigger( 'focus' );
			} else {
				controls[ controlIndex + 1 ].container.find( ':focusable:first' ).focus();
			}
		},
		/**
		 * Handle tabbing to the field before the editor.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		onTabPrevious: function onTabPrevious() {
			var control = this, controls, controlIndex, section;
			section = api.section( control.section() );
			controls = section.controls();
			controlIndex = controls.indexOf( control );
			if ( 0 === controlIndex ) {
				section.contentContainer.find( '.customize-section-title .customize-help-toggle, .customize-section-title .customize-section-description.open .section-description-close' ).last().focus();
			} else {
				controls[ controlIndex - 1 ].contentContainer.find( ':focusable:first' ).focus();
			}
		},
		/**
		 * Update error notice.
		 *
		 * @since 4.9.0
		 * @param {Array} errorAnnotations - Error annotations.
		 * @return {void}
		 */
		onUpdateErrorNotice: function onUpdateErrorNotice( errorAnnotations ) {
			var control = this, message;
			control.setting.notifications.remove( 'csslint_error' );
			if ( 0 !== errorAnnotations.length ) {
				if ( 1 === errorAnnotations.length ) {
					message = api.l10n.customCssError.singular.replace( '%d', '1' );
				} else {
					message = api.l10n.customCssError.plural.replace( '%d', String( errorAnnotations.length ) );
				}
				control.setting.notifications.add( new api.Notification( 'csslint_error', {
					message: message,
					type: 'error'
				} ) );
			}
		},
		/**
		 * Initialize plain-textarea editor when syntax highlighting is disabled.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		initPlainTextareaEditor: function() {
			var control = this, $textarea = control.container.find( 'textarea' ), textarea = $textarea[0];
			$textarea.on( 'blur', function onBlur() {
				$textarea.data( 'next-tab-blurs', false );
			} );
			$textarea.on( 'keydown', function onKeydown( event ) {
				var selectionStart, selectionEnd, value, tabKeyCode = 9, escKeyCode = 27;
				if ( escKeyCode === event.keyCode ) {
					if ( ! $textarea.data( 'next-tab-blurs' ) ) {
						$textarea.data( 'next-tab-blurs', true );
						event.stopPropagation(); // Prevent collapsing the section.
					}
					return;
				}
				// Short-circuit if tab key is not being pressed or if a modifier key *is* being pressed.
				if ( tabKeyCode !== event.keyCode || event.ctrlKey || event.altKey || event.shiftKey ) {
					return;
				}
				// Prevent capturing Tab characters if Esc was pressed.
				if ( $textarea.data( 'next-tab-blurs' ) ) {
					return;
				}
				selectionStart = textarea.selectionStart;
				selectionEnd = textarea.selectionEnd;
				value = textarea.value;
				if ( selectionStart >= 0 ) {
					textarea.value = value.substring( 0, selectionStart ).concat( '\t', value.substring( selectionEnd ) );
					$textarea.selectionStart = textarea.selectionEnd = selectionStart + 1;
				}
				event.stopPropagation();
				event.preventDefault();
			});
			control.deferred.codemirror.rejectWith( control );
		}
	});
	/**
	 * Class wp.customize.DateTimeControl.
	 *
	 * @since 4.9.0
	 * @class    wp.customize.DateTimeControl
	 * @augments wp.customize.Control
	 */
	api.DateTimeControl = api.Control.extend(/** @lends wp.customize.DateTimeControl.prototype */{
		/**
		 * Initialize behaviors.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		ready: function ready() {
			var control = this;
			control.inputElements = {};
			control.invalidDate = false;
			_.bindAll( control, 'populateSetting', 'updateDaysForMonth', 'populateDateInputs' );
			if ( ! control.setting ) {
				throw new Error( 'Missing setting' );
			}
			control.container.find( '.date-input' ).each( function() {
				var input = $( this ), component, element;
				component = input.data( 'component' );
				element = new api.Element( input );
				control.inputElements[ component ] = element;
				control.elements.push( element );
				// Add invalid date error once user changes (and has blurred the input).
				input.on( 'change', function() {
					if ( control.invalidDate ) {
						control.notifications.add( new api.Notification( 'invalid_date', {
							message: api.l10n.invalidDate
						} ) );
					}
				} );
				// Remove the error immediately after validity change.
				input.on( 'input', _.debounce( function() {
					if ( ! control.invalidDate ) {
						control.notifications.remove( 'invalid_date' );
					}
				} ) );
				// Add zero-padding when blurring field.
				input.on( 'blur', _.debounce( function() {
					if ( ! control.invalidDate ) {
						control.populateDateInputs();
					}
				} ) );
			} );
			control.inputElements.month.bind( control.updateDaysForMonth );
			control.inputElements.year.bind( control.updateDaysForMonth );
			control.populateDateInputs();
			control.setting.bind( control.populateDateInputs );
			// Start populating setting after inputs have been populated.
			_.each( control.inputElements, function( element ) {
				element.bind( control.populateSetting );
			} );
		},
		/**
		 * Parse datetime string.
		 *
		 * @since 4.9.0
		 *
		 * @param {string} datetime - Date/Time string. Accepts Y-m-d[ H:i[:s]] format.
		 * @return {Object|null} Returns object containing date components or null if parse error.
		 */
		parseDateTime: function parseDateTime( datetime ) {
			var control = this, matches, date, midDayHour = 12;
			if ( datetime ) {
				matches = datetime.match( /^(\d\d\d\d)-(\d\d)-(\d\d)(?: (\d\d):(\d\d)(?::(\d\d))?)?$/ );
			}
			if ( ! matches ) {
				return null;
			}
			matches.shift();
			date = {
				year: matches.shift(),
				month: matches.shift(),
				day: matches.shift(),
				hour: matches.shift() || '00',
				minute: matches.shift() || '00',
				second: matches.shift() || '00'
			};
			if ( control.params.includeTime && control.params.twelveHourFormat ) {
				date.hour = parseInt( date.hour, 10 );
				date.meridian = date.hour >= midDayHour ? 'pm' : 'am';
				date.hour = date.hour % midDayHour ? String( date.hour % midDayHour ) : String( midDayHour );
				delete date.second; // @todo Why only if twelveHourFormat?
			}
			return date;
		},
		/**
		 * Validates if input components have valid date and time.
		 *
		 * @since 4.9.0
		 * @return {boolean} If date input fields has error.
		 */
		validateInputs: function validateInputs() {
			var control = this, components, validityInput;
			control.invalidDate = false;
			components = [ 'year', 'day' ];
			if ( control.params.includeTime ) {
				components.push( 'hour', 'minute' );
			}
			_.find( components, function( component ) {
				var element, max, min, value;
				element = control.inputElements[ component ];
				validityInput = element.element.get( 0 );
				max = parseInt( element.element.attr( 'max' ), 10 );
				min = parseInt( element.element.attr( 'min' ), 10 );
				value = parseInt( element(), 10 );
				control.invalidDate = isNaN( value ) || value > max || value < min;
				if ( ! control.invalidDate ) {
					validityInput.setCustomValidity( '' );
				}
				return control.invalidDate;
			} );
			if ( control.inputElements.meridian && ! control.invalidDate ) {
				validityInput = control.inputElements.meridian.element.get( 0 );
				if ( 'am' !== control.inputElements.meridian.get() && 'pm' !== control.inputElements.meridian.get() ) {
					control.invalidDate = true;
				} else {
					validityInput.setCustomValidity( '' );
				}
			}
			if ( control.invalidDate ) {
				validityInput.setCustomValidity( api.l10n.invalidValue );
			} else {
				validityInput.setCustomValidity( '' );
			}
			if ( ! control.section() || api.section.has( control.section() ) && api.section( control.section() ).expanded() ) {
				_.result( validityInput, 'reportValidity' );
			}
			return control.invalidDate;
		},
		/**
		 * Updates number of days according to the month and year selected.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		updateDaysForMonth: function updateDaysForMonth() {
			var control = this, daysInMonth, year, month, day;
			month = parseInt( control.inputElements.month(), 10 );
			year = parseInt( control.inputElements.year(), 10 );
			day = parseInt( control.inputElements.day(), 10 );
			if ( month && year ) {
				daysInMonth = new Date( year, month, 0 ).getDate();
				control.inputElements.day.element.attr( 'max', daysInMonth );
				if ( day > daysInMonth ) {
					control.inputElements.day( String( daysInMonth ) );
				}
			}
		},
		/**
		 * Populate setting value from the inputs.
		 *
		 * @since 4.9.0
		 * @return {boolean} If setting updated.
		 */
		populateSetting: function populateSetting() {
			var control = this, date;
			if ( control.validateInputs() || ! control.params.allowPastDate && ! control.isFutureDate() ) {
				return false;
			}
			date = control.convertInputDateToString();
			control.setting.set( date );
			return true;
		},
		/**
		 * Converts input values to string in Y-m-d H:i:s format.
		 *
		 * @since 4.9.0
		 * @return {string} Date string.
		 */
		convertInputDateToString: function convertInputDateToString() {
			var control = this, date = '', dateFormat, hourInTwentyFourHourFormat,
				getElementValue, pad;
			pad = function( number, padding ) {
				var zeros;
				if ( String( number ).length < padding ) {
					zeros = padding - String( number ).length;
					number = Math.pow( 10, zeros ).toString().substr( 1 ) + String( number );
				}
				return number;
			};
			getElementValue = function( component ) {
				var value = parseInt( control.inputElements[ component ].get(), 10 );
				if ( _.contains( [ 'month', 'day', 'hour', 'minute' ], component ) ) {
					value = pad( value, 2 );
				} else if ( 'year' === component ) {
					value = pad( value, 4 );
				}
				return value;
			};
			dateFormat = [ 'year', '-', 'month', '-', 'day' ];
			if ( control.params.includeTime ) {
				hourInTwentyFourHourFormat = control.inputElements.meridian ? control.convertHourToTwentyFourHourFormat( control.inputElements.hour(), control.inputElements.meridian() ) : control.inputElements.hour();
				dateFormat = dateFormat.concat( [ ' ', pad( hourInTwentyFourHourFormat, 2 ), ':', 'minute', ':', '00' ] );
			}
			_.each( dateFormat, function( component ) {
				date += control.inputElements[ component ] ? getElementValue( component ) : component;
			} );
			return date;
		},
		/**
		 * Check if the date is in the future.
		 *
		 * @since 4.9.0
		 * @return {boolean} True if future date.
		 */
		isFutureDate: function isFutureDate() {
			var control = this;
			return 0 < api.utils.getRemainingTime( control.convertInputDateToString() );
		},
		/**
		 * Convert hour in twelve hour format to twenty four hour format.
		 *
		 * @since 4.9.0
		 * @param {string} hourInTwelveHourFormat - Hour in twelve hour format.
		 * @param {string} meridian - Either 'am' or 'pm'.
		 * @return {string} Hour in twenty four hour format.
		 */
		convertHourToTwentyFourHourFormat: function convertHour( hourInTwelveHourFormat, meridian ) {
			var hourInTwentyFourHourFormat, hour, midDayHour = 12;
			hour = parseInt( hourInTwelveHourFormat, 10 );
			if ( isNaN( hour ) ) {
				return '';
			}
			if ( 'pm' === meridian && hour < midDayHour ) {
				hourInTwentyFourHourFormat = hour + midDayHour;
			} else if ( 'am' === meridian && midDayHour === hour ) {
				hourInTwentyFourHourFormat = hour - midDayHour;
			} else {
				hourInTwentyFourHourFormat = hour;
			}
			return String( hourInTwentyFourHourFormat );
		},
		/**
		 * Populates date inputs in date fields.
		 *
		 * @since 4.9.0
		 * @return {boolean} Whether the inputs were populated.
		 */
		populateDateInputs: function populateDateInputs() {
			var control = this, parsed;
			parsed = control.parseDateTime( control.setting.get() );
			if ( ! parsed ) {
				return false;
			}
			_.each( control.inputElements, function( element, component ) {
				var value = parsed[ component ]; // This will be zero-padded string.
				// Set month and meridian regardless of focused state since they are dropdowns.
				if ( 'month' === component || 'meridian' === component ) {
					// Options in dropdowns are not zero-padded.
					value = value.replace( /^0/, '' );
					element.set( value );
				} else {
					value = parseInt( value, 10 );
					if ( ! element.element.is( document.activeElement ) ) {
						// Populate element with zero-padded value if not focused.
						element.set( parsed[ component ] );
					} else if ( value !== parseInt( element(), 10 ) ) {
						// Forcibly update the value if its underlying value changed, regardless of zero-padding.
						element.set( String( value ) );
					}
				}
			} );
			return true;
		},
		/**
		 * Toggle future date notification for date control.
		 *
		 * @since 4.9.0
		 * @param {boolean} notify Add or remove the notification.
		 * @return {wp.customize.DateTimeControl}
		 */
		toggleFutureDateNotification: function toggleFutureDateNotification( notify ) {
			var control = this, notificationCode, notification;
			notificationCode = 'not_future_date';
			if ( notify ) {
				notification = new api.Notification( notificationCode, {
					type: 'error',
					message: api.l10n.futureDateError
				} );
				control.notifications.add( notification );
			} else {
				control.notifications.remove( notificationCode );
			}
			return control;
		}
	});
	/**
	 * Class PreviewLinkControl.
	 *
	 * @since 4.9.0
	 * @class    wp.customize.PreviewLinkControl
	 * @augments wp.customize.Control
	 */
	api.PreviewLinkControl = api.Control.extend(/** @lends wp.customize.PreviewLinkControl.prototype */{
		defaults: _.extend( {}, api.Control.prototype.defaults, {
			templateId: 'customize-preview-link-control'
		} ),
		/**
		 * Initialize behaviors.
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		ready: function ready() {
			var control = this, element, component, node, url, input, button;
			_.bindAll( control, 'updatePreviewLink' );
			if ( ! control.setting ) {
			    control.setting = new api.Value();
			}
			control.previewElements = {};
			control.container.find( '.preview-control-element' ).each( function() {
				node = $( this );
				component = node.data( 'component' );
				element = new api.Element( node );
				control.previewElements[ component ] = element;
				control.elements.push( element );
			} );
			url = control.previewElements.url;
			input = control.previewElements.input;
			button = control.previewElements.button;
			input.link( control.setting );
			url.link( control.setting );
			url.bind( function( value ) {
				url.element.parent().attr( {
					href: value,
					target: api.settings.changeset.uuid
				} );
			} );
			api.bind( 'ready', control.updatePreviewLink );
			api.state( 'saved' ).bind( control.updatePreviewLink );
			api.state( 'changesetStatus' ).bind( control.updatePreviewLink );
			api.state( 'activated' ).bind( control.updatePreviewLink );
			api.previewer.previewUrl.bind( control.updatePreviewLink );
			button.element.on( 'click', function( event ) {
				event.preventDefault();
				if ( control.setting() ) {
					input.element.select();
					document.execCommand( 'copy' );
					button( button.element.data( 'copied-text' ) );
				}
			} );
			url.element.parent().on( 'click', function( event ) {
				if ( $( this ).hasClass( 'disabled' ) ) {
					event.preventDefault();
				}
			} );
			button.element.on( 'mouseenter', function() {
				if ( control.setting() ) {
					button( button.element.data( 'copy-text' ) );
				}
			} );
		},
		/**
		 * Updates Preview Link
		 *
		 * @since 4.9.0
		 * @return {void}
		 */
		updatePreviewLink: function updatePreviewLink() {
			var control = this, unsavedDirtyValues;
			unsavedDirtyValues = ! api.state( 'saved' ).get() || '' === api.state( 'changesetStatus' ).get() || 'auto-draft' === api.state( 'changesetStatus' ).get();
			control.toggleSaveNotification( unsavedDirtyValues );
			control.previewElements.url.element.parent().toggleClass( 'disabled', unsavedDirtyValues );
			control.previewElements.button.element.prop( 'disabled', unsavedDirtyValues );
			control.setting.set( api.previewer.getFrontendPreviewUrl() );
		},
		/**
		 * Toggles save notification.
		 *
		 * @since 4.9.0
		 * @param {boolean} notify Add or remove notification.
		 * @return {void}
		 */
		toggleSaveNotification: function toggleSaveNotification( notify ) {
			var control = this, notificationCode, notification;
			notificationCode = 'changes_not_saved';
			if ( notify ) {
				notification = new api.Notification( notificationCode, {
					type: 'info',
					message: api.l10n.saveBeforeShare
				} );
				control.notifications.add( notification );
			} else {
				control.notifications.remove( notificationCode );
			}
		}
	});
	/**
	 * Change objects contained within the main customize object to Settings.
	 *
	 * @alias wp.customize.defaultConstructor
	 */
	api.defaultConstructor = api.Setting;
	/**
	 * Callback for resolved controls.
	 *
	 * @callback wp.customize.deferredControlsCallback
	 * @param {wp.customize.Control[]} controls Resolved controls.
	 */
	/**
	 * Collection of all registered controls.
	 *
	 * @alias wp.customize.control
	 *
	 * @since 3.4.0
	 *
	 * @type {Function}
	 * @param {...string} ids - One or more ids for controls to obtain.
	 * @param {deferredControlsCallback} [callback] - Function called when all supplied controls exist.
	 * @return {wp.customize.Control|undefined|jQuery.promise} Control instance or undefined (if function called with one id param),
	 *                                                         or promise resolving to requested controls.
	 *
	 * @example Loop over all registered controls.
	 * wp.customize.control.each( function( control ) { ... } );
	 *
	 * @example Getting `background_color` control instance.
	 * control = wp.customize.control( 'background_color' );
	 *
	 * @example Check if control exists.
	 * hasControl = wp.customize.control.has( 'background_color' );
	 *
	 * @example Deferred getting of `background_color` control until it exists, using callback.
	 * wp.customize.control( 'background_color', function( control ) { ... } );
	 *
	 * @example Get title and tagline controls when they both exist, using promise (only available when multiple IDs are present).
	 * promise = wp.customize.control( 'blogname', 'blogdescription' );
	 * promise.done( function( titleControl, taglineControl ) { ... } );
	 *
	 * @example Get title and tagline controls when they both exist, using callback.
	 * wp.customize.control( 'blogname', 'blogdescription', function( titleControl, taglineControl ) { ... } );
	 *
	 * @example Getting setting value for `background_color` control.
	 * value = wp.customize.control( 'background_color ').setting.get();
	 * value = wp.customize( 'background_color' ).get(); // Same as above, since setting ID and control ID are the same.
	 *
	 * @example Add new control for site title.
	 * wp.customize.control.add( new wp.customize.Control( 'other_blogname', {
	 *     setting: 'blogname',
	 *     type: 'text',
	 *     label: 'Site title',
	 *     section: 'other_site_identify'
	 * } ) );
	 *
	 * @example Remove control.
	 * wp.customize.control.remove( 'other_blogname' );
	 *
	 * @example Listen for control being added.
	 * wp.customize.control.bind( 'add', function( addedControl ) { ... } )
	 *
	 * @example Listen for control being removed.
	 * wp.customize.control.bind( 'removed', function( removedControl ) { ... } )
	 */
	api.control = new api.Values({ defaultConstructor: api.Control });
	/**
	 * Callback for resolved sections.
	 *
	 * @callback wp.customize.deferredSectionsCallback
	 * @param {wp.customize.Section[]} sections Resolved sections.
	 */
	/**
	 * Collection of all registered sections.
	 *
	 * @alias wp.customize.section
	 *
	 * @since 3.4.0
	 *
	 * @type {Function}
	 * @param {...string} ids - One or more ids for sections to obtain.
	 * @param {deferredSectionsCallback} [callback] - Function called when all supplied sections exist.
	 * @return {wp.customize.Section|undefined|jQuery.promise} Section instance or undefined (if function called with one id param),
	 *                                                         or promise resolving to requested sections.
	 *
	 * @example Loop over all registered sections.
	 * wp.customize.section.each( function( section ) { ... } )
	 *
	 * @example Getting `title_tagline` section instance.
	 * section = wp.customize.section( 'title_tagline' )
	 *
	 * @example Expand dynamically-created section when it exists.
	 * wp.customize.section( 'dynamically_created', function( section ) {
	 *     section.expand();
	 * } );
	 *
	 * @see {@link wp.customize.control} for further examples of how to interact with {@link wp.customize.Values} instances.
	 */
	api.section = new api.Values({ defaultConstructor: api.Section });
	/**
	 * Callback for resolved panels.
	 *
	 * @callback wp.customize.deferredPanelsCallback
	 * @param {wp.customize.Panel[]} panels Resolved panels.
	 */
	/**
	 * Collection of all registered panels.
	 *
	 * @alias wp.customize.panel
	 *
	 * @since 4.0.0
	 *
	 * @type {Function}
	 * @param {...string} ids - One or more ids for panels to obtain.
	 * @param {deferredPanelsCallback} [callback] - Function called when all supplied panels exist.
	 * @return {wp.customize.Panel|undefined|jQuery.promise} Panel instance or undefined (if function called with one id param),
	 *                                                       or promise resolving to requested panels.
	 *
	 * @example Loop over all registered panels.
	 * wp.customize.panel.each( function( panel ) { ... } )
	 *
	 * @example Getting nav_menus panel instance.
	 * panel = wp.customize.panel( 'nav_menus' );
	 *
	 * @example Expand dynamically-created panel when it exists.
	 * wp.customize.panel( 'dynamically_created', function( panel ) {
	 *     panel.expand();
	 * } );
	 *
	 * @see {@link wp.customize.control} for further examples of how to interact with {@link wp.customize.Values} instances.
	 */
	api.panel = new api.Values({ defaultConstructor: api.Panel });
	/**
	 * Callback for resolved notifications.
	 *
	 * @callback wp.customize.deferredNotificationsCallback
	 * @param {wp.customize.Notification[]} notifications Resolved notifications.
	 */
	/**
	 * Collection of all global notifications.
	 *
	 * @alias wp.customize.notifications
	 *
	 * @since 4.9.0
	 *
	 * @type {Function}
	 * @param {...string} codes - One or more codes for notifications to obtain.
	 * @param {deferredNotificationsCallback} [callback] - Function called when all supplied notifications exist.
	 * @return {wp.customize.Notification|undefined|jQuery.promise} Notification instance or undefined (if function called with one code param),
	 *                                                              or promise resolving to requested notifications.
	 *
	 * @example Check if existing notification
	 * exists = wp.customize.notifications.has( 'a_new_day_arrived' );
	 *
	 * @example Obtain existing notification
	 * notification = wp.customize.notifications( 'a_new_day_arrived' );
	 *
	 * @example Obtain notification that may not exist yet.
	 * wp.customize.notifications( 'a_new_day_arrived', function( notification ) { ... } );
	 *
	 * @example Add a warning notification.
	 * wp.customize.notifications.add( new wp.customize.Notification( 'midnight_almost_here', {
	 *     type: 'warning',
	 *     message: 'Midnight has almost arrived!',
	 *     dismissible: true
	 * } ) );
	 *
	 * @example Remove a notification.
	 * wp.customize.notifications.remove( 'a_new_day_arrived' );
	 *
	 * @see {@link wp.customize.control} for further examples of how to interact with {@link wp.customize.Values} instances.
	 */
	api.notifications = new api.Notifications();
	api.PreviewFrame = api.Messenger.extend(/** @lends wp.customize.PreviewFrame.prototype */{
		sensitivity: null, // Will get set to api.settings.timeouts.previewFrameSensitivity.
		/**
		 * An object that fetches a preview in the background of the document, which
		 * allows for seamless replacement of an existing preview.
		 *
		 * @constructs wp.customize.PreviewFrame
		 * @augments   wp.customize.Messenger
		 *
		 * @param {Object} params.container
		 * @param {Object} params.previewUrl
		 * @param {Object} params.query
		 * @param {Object} options
		 */
		initialize: function( params, options ) {
			var deferred = $.Deferred();
			/*
			 * Make the instance of the PreviewFrame the promise object
			 * so other objects can easily interact with it.
			 */
			deferred.promise( this );
			this.container = params.container;
			$.extend( params, { channel: api.PreviewFrame.uuid() });
			api.Messenger.prototype.initialize.call( this, params, options );
			this.add( 'previewUrl', params.previewUrl );
			this.query = $.extend( params.query || {}, { customize_messenger_channel: this.channel() });
			this.run( deferred );
		},
		/**
		 * Run the preview request.
		 *
		 * @param {Object} deferred jQuery Deferred object to be resolved with
		 *                          the request.
		 */
		run: function( deferred ) {
			var previewFrame = this,
				loaded = false,
				ready = false,
				readyData = null,
				hasPendingChangesetUpdate = '{}' !== previewFrame.query.customized,
				urlParser,
				params,
				form;
			if ( previewFrame._ready ) {
				previewFrame.unbind( 'ready', previewFrame._ready );
			}
			previewFrame._ready = function( data ) {
				ready = true;
				readyData = data;
				previewFrame.container.addClass( 'iframe-ready' );
				if ( ! data ) {
					return;
				}
				if ( loaded ) {
					deferred.resolveWith( previewFrame, [ data ] );
				}
			};
			previewFrame.bind( 'ready', previewFrame._ready );
			urlParser = document.createElement( 'a' );
			urlParser.href = previewFrame.previewUrl();
			params = _.extend(
				api.utils.parseQueryString( urlParser.search.substr( 1 ) ),
				{
					customize_changeset_uuid: previewFrame.query.customize_changeset_uuid,
					customize_theme: previewFrame.query.customize_theme,
					customize_messenger_channel: previewFrame.query.customize_messenger_channel
				}
			);
			if ( api.settings.changeset.autosaved || ! api.state( 'saved' ).get() ) {
				params.customize_autosaved = 'on';
			}
			urlParser.search = $.param( params );
			previewFrame.iframe = $( '', {
				title: api.l10n.previewIframeTitle,
				name: 'customize-' + previewFrame.channel()
			} );
			previewFrame.iframe.attr( 'onmousewheel', '' ); // Workaround for Safari bug. See WP Trac #38149.
			previewFrame.iframe.attr( 'sandbox', 'allow-forms allow-modals allow-orientation-lock allow-pointer-lock allow-popups allow-popups-to-escape-sandbox allow-presentation allow-same-origin allow-scripts' );
			if ( ! hasPendingChangesetUpdate ) {
				previewFrame.iframe.attr( 'src', urlParser.href );
			} else {
				previewFrame.iframe.attr( 'data-src', urlParser.href ); // For debugging purposes.
			}
			previewFrame.iframe.appendTo( previewFrame.container );
			previewFrame.targetWindow( previewFrame.iframe[0].contentWindow );
			/*
			 * Submit customized data in POST request to preview frame window since
			 * there are setting value changes not yet written to changeset.
			 */
			if ( hasPendingChangesetUpdate ) {
				form = $( '