Add support for highlighting menu items

chrome/android/java/src/org/chromium/chrome/browser/appmenu/AppMenuObserver.java

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.appmenu;
 
 /**
  * Allows monitoring of application menu actions.
  */
 public interface AppMenuObserver {
     /**
      * Informs when the App Menu visibility changes.
      * @param isVisible Whether the menu is now visible.
      */
     public void onMenuVisibilityChanged(boolean isVisible);
+
+    /**
+     * Note that this will be called with {@code false} once the menu is opened.
+     * @param highlighting Whether or not the menu is highlighting (or planning to highlight) an
+     *                     item.
+     */
+    public void onMenuHighlightChanged(boolean highlighting);
 }