Media Grid: when the modal is open, don't respond to arrow keys when `<textarea>` has focus.

Merges [29777] (and [30378]) to the 4.0 branch.

Props ryelle, adamsilverstein.
Fixes #29725.

Built from https://develop.svn.wordpress.org/branches/4.0@30407


git-svn-id: http://core.svn.wordpress.org/branches/4.0@30402 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/js/media-grid.js

@@ -577,10 +577,11 @@
 			return ( this.getCurrentIndex() - 1 ) > -1;
 		},
 		/**
-		 * Respond to the keyboard events: right arrow, left arrow, escape.
+		 * Respond to the keyboard events: right arrow, left arrow, except when
+		 * focus is in a textarea or input field.
 		 */
 		keyEvent: function( event ) {
-			if ( 'INPUT' === event.target.tagName && ! ( event.target.readOnly || event.target.disabled ) ) {
+			if ( ( 'INPUT' === event.target.nodeName || 'TEXTAREA' === event.target.nodeName ) && ! ( event.target.readOnly || event.target.disabled ) ) {
 				return;
 			}