Move the Notification browser tests down to //content.

content/test/notifications/service_worker.js

-// Copyright 2014 The Chromium Authors. All rights reserved.
+// 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.
 
-// Service Worker to be used with the platform_notification_service.html page.
+// Service Worker to be used with the test.html page.
 var messagePort = null;
 
 addEventListener('message', function (event) {
   messagePort = event.data;
   messagePort.postMessage('ready');
 });
 
 // The notificationclick event will be invoked when a persistent notification
 // has been clicked on. When this happens, the title determines whether this
 // Service Worker has to act upon this.
 addEventListener('notificationclick', function (event) {
   if (event.notification.title == 'action_close')
     event.notification.close();
 
   messagePort.postMessage(event.notification.title);
 });