MDL-41328 Editor: Work around another iOS issue with TinyMCE

We apply this only on touchend and not touchstart or touchmove. The
location is not guaranteed until the end of the gesture, and there's no
need to keep applying focus on every move.

lib/editor/tinymce/module.js

@@ -68,6 +68,13 @@ M.editor_tinymce.init_editor = function(Y, editorid, options) {
                 ed.contentDocument.addEventListener('keydown', function() {
                     ed.contentWindow.focus();
                 });
+
+                // Whenever a touch event is registered against the content document,
+                // reapply focus. This works around an issue with the location caret not
+                // being focusable without use of the Loupe.
+                ed.contentDocument.addEventListener('touchend', function() {
+                    ed.contentWindow.focus();
+                });
             });
         };
     }