Customizer: Passes focus to the upload tab to avoid focus changing when a drag event occurs from outside the browser. props lessbloat. fixes #21283.

git-svn-id: https://develop.svn.wordpress.org/trunk@22512 602fd350-edb4-49c9-b593-d223f7449a82

wp-admin/js/customize-controls.js

@@ -104,6 +104,9 @@
 				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 () {