Hooking up Android N inline notification replies end-to-end

chrome/test/data/notifications/notification_test_utils.js

 // Copyright 2015 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.
 
 var activatedServiceWorkerPromise = null;
+var messagePort = null;
 
 // Returns a promise that will be resolved with an activated Service
 // Worker, or rejects when the Service Worker could not be started. There
 // will be a message port to and from the worker in |messagePort|.
 function GetActivatedServiceWorker(script, scope) {
   if (activatedServiceWorkerPromise == null) {
     activatedServiceWorkerPromise =
         navigator.serviceWorker.getRegistration(scope)
         .then(function(registration) {
           // Unregister any existing Service Worker.
@@ skipping 28 matching lines @@
                                             [ channel.port2 ]);
 
             messagePort = channel.port1;
             messagePort.start();
           });
         });
   }
 
   return activatedServiceWorkerPromise;
 }