Add paper-menu-button and its dependencies to third_party/polymer

third_party/polymer/v1_0/components-chromium/iron-pages/iron-pages-extracted.js

 
 
   Polymer({
 
     is: 'iron-pages',
 
     behaviors: [
       Polymer.IronResizableBehavior,
       Polymer.IronSelectableBehavior
     ],
 
     properties: {
 
       // as the selected page is the only one visible, activateEvent
       // is both non-sensical and problematic; e.g. in cases where a user
       // handler attempts to change the page and the activateEvent
       // handler immediately changes it back
       activateEvent: {
+        type: String,
         value: null
       }
 
     },
 
     observers: [
       '_selectedPageChanged(selected)'
     ],
 
     _selectedPageChanged: function(selected, old) {
       this.async(this.notifyResize);
     }
   });