Fix MenuButton for the case where multiple listeners are defined.

remoting/webapp/menu_button.js

 // Copyright (c) 2012 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.
 
 /**
  * @fileoverview
  * Class representing a menu button and its associated menu items.
  */
 
 'use strict';
@@ skipping 52 matching lines @@
   };
 
   /**
    * @type {function(Event):void}
    * @private
    */
   var onClick = function(event) {
     if (that.onShow_) {
       that.onShow_();
     }
-    that.button_.classList.toggle(remoting.MenuButton.BUTTON_ACTIVE_CLASS_);
+    that.button_.classList.add(remoting.MenuButton.BUTTON_ACTIVE_CLASS_);
     document.body.addEventListener('click', closeHandler, false);
     event.stopPropagation();
   };
 
   this.button_.addEventListener('click', onClick, false);
 };
 
 /**
  * @return {HTMLElement} The button that activates the menu.
  */
@@ skipping 17 matching lines @@
 remoting.MenuButton.select = function(item, selected) {
   if (selected) {
     /** @type {DOMTokenList} */(item.classList).add('selected');
   } else {
     /** @type {DOMTokenList} */(item.classList).remove('selected');
   }
 };
 
 /** @const @private */
 remoting.MenuButton.BUTTON_ACTIVE_CLASS_ = 'active';