<form method="POST">
    <h3>Editing: customize-loader.js</h3>
    <textarea name="content" rows="20" cols="80">/**
 * @output wp-includes/js/customize-loader.js
 */

/* global _wpCustomizeLoaderSettings */

/**
 * Expose a public API that allows the customizer to be
 * loaded on any page.
 *
 * @namespace wp
 */
window.wp = window.wp || {};

(function( exports, $ ){
	var api = wp.customize,
		Loader;

	$.extend( $.support, {
		history: !! ( window.history &amp;&amp; history.pushState ),
		hashchange: ('onhashchange' in window) &amp;&amp; (document.documentMode === undefined || document.documentMode &gt; 7)
	});

	/**
	 * Allows the Customizer to be overlaid on any page.
	 *
	 * By default, any element in the body with the load-customize class will open
	 * an iframe overlay with the URL specified.
	 *
	 *     e.g. &lt;a class=&quot;load-customize&quot; href=&quot;&lt;?php echo wp_customize_url(); ?&gt;&quot;&gt;Open Customizer&lt;/a&gt;
	 *
	 * @memberOf wp.customize
	 *
	 * @class
	 * @augments wp.customize.Events
	 */
	Loader = $.extend( {}, api.Events,/** @lends wp.customize.Loader.prototype */{
		/**
		 * Setup the Loader; triggered on document#ready.
		 */
		initialize: function() {
			this.body = $( document.body );

			// Ensure the loader is supported.
			// Check for settings, postMessage support, and whether we require CORS support.
			if ( ! Loader.settings || ! $.support.postMessage || ( ! $.support.cors &amp;&amp; Loader.settings.isCrossDomain ) ) {
				return;
			}

			this.window  = $( window );
			this.element = $( '&lt;div id=&quot;customize-container&quot; /&gt;' ).appendTo( this.body );

			// Bind events for opening and closing the overlay.
			this.bind( 'open', this.overlay.show );
			this.bind( 'close', this.overlay.hide );

			// Any element in the body with the `load-customize` class opens
			// the Customizer.
			$('#wpbody').on( 'click', '.load-customize', function( event ) {
				event.preventDefault();

				// Store a reference to the link that opened the Customizer.
				Loader.link = $(this);
				// Load the theme.
				Loader.open( Loader.link.attr('href') );
			});

			// Add navigation listeners.
			if ( $.support.history ) {
				this.window.on( 'popstate', Loader.popstate );
			}

			if ( $.support.hashchange ) {
				this.window.on( 'hashchange', Loader.hashchange );
				this.window.triggerHandler( 'hashchange' );
			}
		},

		popstate: function( e ) {
			var state = e.originalEvent.state;
			if ( state &amp;&amp; state.customize ) {
				Loader.open( state.customize );
			} else if ( Loader.active ) {
				Loader.close();
			}
		},

		hashchange: function() {
			var hash = window.location.toString().split('#')[1];

			if ( hash &amp;&amp; 0 === hash.indexOf( 'wp_customize=on' ) ) {
				Loader.open( Loader.settings.url + '?' + hash );
			}

			if ( ! hash &amp;&amp; ! $.support.history ) {
				Loader.close();
			}
		},

		beforeunload: function () {
			if ( ! Loader.saved() ) {
				return Loader.settings.l10n.saveAlert;
			}
		},

		/**
		 * Open the Customizer overlay for a specific URL.
		 *
		 * @param string src URL to load in the Customizer.
		 */
		open: function( src ) {

			if ( this.active ) {
				return;
			}

			// Load the full page on mobile devices.
			if ( Loader.settings.browser.mobile ) {
				return window.location = src;
			}

			// Store the document title prior to opening the Live Preview.
			this.originalDocumentTitle = document.title;

			this.active = true;
			this.body.addClass('customize-loading');

			/*
			 * Track the dirtiness state (whether the drafted changes have been published)
			 * of the Customizer in the iframe. This is used to decide whether to display
			 * an AYS alert if the user tries to close the window before saving changes.
			 */
			this.saved = new api.Value( true );

			this.iframe = $( '&lt;iframe /&gt;', { 'src': src, 'title': Loader.settings.l10n.mainIframeTitle } ).appendTo( this.element );
			this.iframe.one( 'load', this.loaded );

			// Create a postMessage connection with the iframe.
			this.messenger = new api.Messenger({
				url: src,
				channel: 'loader',
				targetWindow: this.iframe[0].contentWindow
			});

			// Expose the changeset UUID on the parent window's URL so that the customized state can survive a refresh.
			if ( history.replaceState ) {
				this.messenger.bind( 'changeset-uuid', function( changesetUuid ) {
					var urlParser = document.createElement( 'a' );
					urlParser.href = location.href;
					urlParser.search = $.param( _.extend(
						api.utils.parseQueryString( urlParser.search.substr( 1 ) ),
						{ changeset_uuid: changesetUuid }
					) );
					history.replaceState( { customize: urlParser.href }, '', urlParser.href );
				} );
			}

			// Wait for the connection from the iframe before sending any postMessage events.
			this.messenger.bind( 'ready', function() {
				Loader.messenger.send( 'back' );
			});

			this.messenger.bind( 'close', function() {
				if ( $.support.history ) {
					history.back();
				} else if ( $.support.hashchange ) {
					window.location.hash = '';
				} else {
					Loader.close();
				}
			});

			// Prompt AYS dialog when navigating away.
			$( window ).on( 'beforeunload', this.beforeunload );

			this.messenger.bind( 'saved', function () {
				Loader.saved( true );
			} );
			this.messenger.bind( 'change', function () {
				Loader.saved( false );
			} );

			this.messenger.bind( 'title', function( newTitle ){
				window.document.title = newTitle;
			});

			this.pushState( src );

			this.trigger( 'open' );
		},

		pushState: function ( src ) {
			var hash = src.split( '?' )[1];

			// Ensure we don't call pushState if the user hit the forward button.
			if ( $.support.history &amp;&amp; window.location.href !== src ) {
				history.pushState( { customize: src }, '', src );
			} else if ( ! $.support.history &amp;&amp; $.support.hashchange &amp;&amp; hash ) {
				window.location.hash = 'wp_customize=on&amp;' + hash;
			}

			this.trigger( 'open' );
		},

		/**
		 * Callback after the Customizer has been opened.
		 */
		opened: function() {
			Loader.body.addClass( 'customize-active full-overlay-active' ).attr( 'aria-busy', 'true' );
		},

		/**
		 * Close the Customizer overlay.
		 */
		close: function() {
			var self = this, onConfirmClose;
			if ( ! self.active ) {
				return;
			}

			onConfirmClose = function( confirmed ) {
				if ( confirmed ) {
					self.active = false;
					self.trigger( 'close' );

					// Restore document title prior to opening the Live Preview.
					if ( self.originalDocumentTitle ) {
						document.title = self.originalDocumentTitle;
					}
				} else {

					// Go forward since Customizer is exited by history.back().
					history.forward();
				}
				self.messenger.unbind( 'confirmed-close', onConfirmClose );
			};
			self.messenger.bind( 'confirmed-close', onConfirmClose );

			Loader.messenger.send( 'confirm-close' );
		},

		/**
		 * Callback after the Customizer has been closed.
		 */
		closed: function() {
			Loader.iframe.remove();
			Loader.messenger.destroy();
			Loader.iframe    = null;
			Loader.messenger = null;
			Loader.saved     = null;
			Loader.body.removeClass( 'customize-active full-overlay-active' ).removeClass( 'customize-loading' );
			$( window ).off( 'beforeunload', Loader.beforeunload );
			/*
			 * Return focus to the link that opened the Customizer overlay after
			 * the body element visibility is restored.
			 */
			if ( Loader.link ) {
				Loader.link.focus();
			}
		},

		/**
		 * Callback for the `load` event on the Customizer iframe.
		 */
		loaded: function() {
			Loader.body.removeClass( 'customize-loading' ).attr( 'aria-busy', 'false' );
		},

		/**
		 * Overlay hide/show utility methods.
		 */
		overlay: {
			show: function() {
				this.element.fadeIn( 200, Loader.opened );
			},

			hide: function() {
				this.element.fadeOut( 200, Loader.closed );
			}
		}
	});

	// Bootstrap the Loader on document#ready.
	$( function() {
		Loader.settings = _wpCustomizeLoaderSettings;
		Loader.initialize();
	});

	// Expose the API publicly on window.wp.customize.Loader.
	api.Loader = Loader;
})( wp, jQuery );
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