ServiceWorker: Read the blob from SW's response to a fetch event

content/test/data/service_worker/fetch_event.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.
 
 this.onfetch = function(event) {
     var headers = new HeaderMap;
     headers.set('Content-Language', 'fi');
     headers.set('Content-Type', 'text/html; charset=UTF-8');
-    var response = new Response({
+    var blob = new Blob(["This resource is gone. Gone, gone, gone."]);
+    var response = new Response(blob, {
         status: 301,
         statusText: 'Moved Permanently',
         headers: headers
     });
 
     event.respondWith(new Promise(function(r) {
         setTimeout(function() { r(response); }, 5);
     }));
 };