Themes: Remove jQuery dependency from wp-custom-header.js.

In [38985], we used jQuery to trigger a custom event once a video
handler has completed so themes, like Twenty Fourteen, can execute
their own adjustments after the header video has loaded.

This replaces the jQuery `trigger()` method with a native event and
updates Twenty Fourteen accordingly.

Props adamsilverstein, joemcgill.
Fixes #38550.

git-svn-id: https://develop.svn.wordpress.org/trunk@39102 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-content/themes/twentyfourteen/js/functions.js

@@ -105,11 +105,6 @@
 
 			if ( body.is( '.header-image' ) ) {
 
-				// Recaculate the header height when a custom header loads.
-				$( 'body' ).on( 'wp-custom-header-video-loaded', function() {
-					mastheadOffset = $( '#site-header' ).height();
-				} );
-
 				_window.on( 'scroll.twentyfourteen', function() {
 					if ( _window.scrollTop() > mastheadOffset && mastheadHeight < 49 ) {
 						body.addClass( 'masthead-fixed' );
@@ -118,6 +113,12 @@
 					}
 				} );
 
+				// Update masthead offset once a custom header video loads.
+				$( document ).on( 'wp-custom-header-video-loaded', function() {
+					mastheadOffset = $( '#site-header' ).height();
+				} );
+
+
 				// Update masthead offset after a selective refresh.
 				if ( 'undefined' !== typeof wp && wp.customize && wp.customize.selectiveRefresh ) {
 					wp.customize.selectiveRefresh.bind( 'partial-content-rendered', function() {