[MD History] Use proper shadows for cards.

ui/webui/resources/cr_elements/cr_shared_menu/cr_shared_menu.js

 // Copyright 2016 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.
 
 /** Same as paper-menu-button's custom easing cubic-bezier param. */
 var SLIDE_CUBIC_BEZIER = 'cubic-bezier(0.3, 0.95, 0.5, 1)';
 
 Polymer({
   is: 'cr-shared-menu',
 
   behaviors: [Polymer.IronA11yKeysBehavior],
 
   properties: {
     menuOpen: {
       type: Boolean,
       observer: 'menuOpenChanged_',
       value: false,
+      notify: true,
     },
 
     /**
      * The contextual item that this menu was clicked for.
      *  e.g. the data used to render an item in an <iron-list> or <dom-repeat>
      * @type {?Object}
      */
     itemData: {
       type: Object,
       value: null,
@@ skipping 160 matching lines @@
   /**
    * Ensure the menu is reset properly when it is closed by the dropdown (eg,
    * clicking outside).
    * @private
    */
   menuOpenChanged_: function() {
     if (!this.menuOpen)
       this.itemData = null;
   },
 });