[Polymer] Roll polymer to latest version

third_party/polymer/v1_0/components-chromium/iron-test-helpers/iron-test-helpers-extracted.js

 (function(global) {
     'use strict';
 
     var TestHelpers = global.TestHelpers = global.TestHelpers || {};
 
     TestHelpers.flushAsynchronousOperations = flushAsynchronousOperations;
     TestHelpers.forceXIfStamp = forceXIfStamp;
     TestHelpers.fireEvent = fireEvent;
+    TestHelpers.skipUnless = skipUnless;
   })(this);