Push API: Return cached registration if available.

chrome/test/data/push_messaging/push_test.js

 // Copyright 2014 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.
 
 'use strict';
 
 var pushData = new FutureData();
 
 // Sends data back to the test. This must be in response to an earlier
 // request, but it's ok to respond asynchronously. The request blocks until
@@ skipping 43 matching lines @@
 
 // Notification permission has been coalesced with Push permission. After
 // this is granted, Push API registration can succeed.
 function requestNotificationPermission() {
   Notification.requestPermission(function(permission) {
     sendResultToTest('permission status - ' + permission);
   });
 }
 
 function registerServiceWorker() {
+  // The base dir used to resolve service_worker.js and the scope depends on
+  // whether this script is included from an html file in ./, subscope1/, or
+  // subscope2/.
   navigator.serviceWorker.register('service_worker.js', {scope: './'}).then(
       function(swRegistration) {
         sendResultToTest('ok - service worker registered');
       }, sendErrorToTest);
 }
 
 function unregisterServiceWorker() {
   navigator.serviceWorker.getRegistration().then(function(swRegistration) {
     swRegistration.unregister().then(function(result) {
       sendResultToTest('service worker unregistration status: ' + result);
@@ skipping 38 matching lines @@
     sendResultToTest('false - is not controlled');
   }
 }
 
 addEventListener('message', function(event) {
   var message = JSON.parse(event.data);
   if (message.type == 'push') {
     pushData.set(message.data);
   }
 }, false);