[ServiceWorker] Make fetch() method better conformance with the spec.

Source/web/ServiceWorkerGlobalScopeClientImpl.cpp

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 62 matching lines @@
 
 void ServiceWorkerGlobalScopeClientImpl::didHandleFetchEvent(int fetchEventID, PassRefPtrWillBeRawPtr<Response> response)
 {
     if (!response) {
         m_client.didHandleFetchEvent(fetchEventID);
         return;
     }
 
     WebServiceWorkerResponse webResponse;
     response->populateWebServiceWorkerResponse(webResponse);
+    if (webResponse.status() == 0) {
+        // The status code is 0 means a network error.
+        m_client.didHandleFetchEvent(fetchEventID);
+        return;
+    }
     m_client.didHandleFetchEvent(fetchEventID, webResponse);
 }
 
 void ServiceWorkerGlobalScopeClientImpl::didHandleSyncEvent(int syncEventID)
 {
     m_client.didHandleSyncEvent(syncEventID);
 }
 
 void ServiceWorkerGlobalScopeClientImpl::postMessageToClient(int clientID, const WebString& message, PassOwnPtr<WebMessagePortChannelArray> webChannels)
 {
     m_client.postMessageToClient(clientID, message, webChannels.leakPtr());
 }
 
 ServiceWorkerGlobalScopeClientImpl::ServiceWorkerGlobalScopeClientImpl(WebServiceWorkerContextClient& client)
     : m_client(client)
 {
 }
 
 } // namespace blink