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

content/test/data/service_worker/sync.js

Index: content/test/data/service_worker/sync.js
diff --git a/content/test/data/service_worker/sync.js b/content/test/data/service_worker/sync.js
index 02da273ab376646fe4f4c2fd0bc282ec0bd2116f..941ea2de93710030097e7f97825fbe0c9a73e2d1 100644
--- a/content/test/data/service_worker/sync.js
+++ b/content/test/data/service_worker/sync.js
@@ -5,7 +5,7 @@
 var code = 404;
 
 this.onfetch = function(event) {
-    response = new Response({
+    response = new Response(new Blob(), {
         status: code,
         statusText: 'OK'
     });