Customize: Add workaround for Safari bug causing preview frame to be unscrollable via `mousewheel` after a refresh.

Props westonruter, tristangemus.
Fixes #38149.

Built from https://develop.svn.wordpress.org/trunk@38742


git-svn-id: http://core.svn.wordpress.org/trunk@38685 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/js/customize-controls.js

@@ -3105,6 +3105,7 @@
 
 				// Create the iframe and inject the html content.
 				self.iframe = $( '<iframe />', { 'title': api.l10n.previewIframeTitle } ).appendTo( self.container );
+				self.iframe.attr( 'onmousewheel', '' ); // Workaround for Safari bug. See WP Trac #38149.
 
 				// Bind load event after the iframe has been added to the page;
 				// otherwise it will fire when injected into the DOM.

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-alpha-38741';
+$wp_version = '4.7-alpha-38742';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.