When switching to the Text editor, make the textarea visible to screen readers.

props afercia.
fixes #29815.
Built from https://develop.svn.wordpress.org/trunk@29815


git-svn-id: http://core.svn.wordpress.org/trunk@29581 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/js/editor.js

@@ -76,6 +76,7 @@ window.switchEditors = {
 
 			DOM.removeClass( wrap_id, 'html-active' );
 			DOM.addClass( wrap_id, 'tmce-active' );
+			DOM.setAttrib( txtarea_el, 'aria-hidden', true );
 			setUserSetting( 'editor', 'tinymce' );
 
 		} else if ( 'html' === mode ) {
@@ -112,6 +113,7 @@ window.switchEditors = {
 
 			DOM.removeClass( wrap_id, 'tmce-active' );
 			DOM.addClass( wrap_id, 'html-active' );
+			DOM.setAttrib( txtarea_el, 'aria-hidden', false );
 			setUserSetting( 'editor', 'html' );
 		}
 		return false;