Move the Notification browser tests down to //content.

content/test/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.
 
 // 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) {
   return navigator.serviceWorker.getRegistration(scope)
       .then(function(registration) {
@@ skipping 26 matching lines @@
           });
 
           registration.active.postMessage(channel.port2,
                                           [ channel.port2 ]);
 
           messagePort = channel.port1;
           messagePort.start();
         });
       });
 }