Use hidden attribute rather the 'display: none' for hiding menus.

chrome/browser/resources/shared/js/cr/ui/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.
 
 cr.define('cr.ui', function() {
   /** @const */
   var Menu = cr.ui.Menu;
   /** @const */
   var positionPopupAroundElement = cr.ui.positionPopupAroundElement;
 
@@ skipping 95 matching lines @@
           break;
       }
     },
 
     /**
      * Shows the menu.
      */
     showMenu: function() {
       this.hideMenu();
 
-      this.menu.style.display = 'block';
+      this.menu.hidden = false;
       this.setAttribute('menu-shown', '');
 
       // when the menu is shown we steal all keyboard events.
       var doc = this.ownerDocument;
       var win = doc.defaultView;
       this.showingEvents_.add(doc, 'keydown', this, true);
       this.showingEvents_.add(doc, 'mousedown', this, true);
       this.showingEvents_.add(doc, 'blur', this, true);
       this.showingEvents_.add(win, 'resize', this);
       this.showingEvents_.add(this.menu, 'activate', this);
       this.positionMenu_();
     },
 
     /**
      * Hides the menu. If your menu can go out of scope, make sure to call this
      * first.
      */
     hideMenu: function() {
       if (!this.isMenuShown())
         return;
 
       this.removeAttribute('menu-shown');
-      this.menu.style.display = 'none';
+      this.menu.hidden = true;
 
       this.showingEvents_.removeAll();
       this.menu.selectedIndex = -1;
     },
 
     /**
      * Whether the menu is shown.
      */
     isMenuShown: function() {
       return this.hasAttribute('menu-shown');
@@ skipping 74 matching lines @@
         'drop-down-arrow-hover', ARROW_WIDTH, ARROW_HEIGHT, hoverColor);
     createDropDownArrowCanvas(
         'drop-down-arrow-active', ARROW_WIDTH, ARROW_HEIGHT, activeColor);
   }
 
   // Export
   return {
     MenuButton: MenuButton
   };
 });