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

Source/web/ServiceWorkerGlobalScopeClientImpl.cpp

Index: Source/web/ServiceWorkerGlobalScopeClientImpl.cpp
diff --git a/Source/web/ServiceWorkerGlobalScopeClientImpl.cpp b/Source/web/ServiceWorkerGlobalScopeClientImpl.cpp
index 8a4d5c1806fa804d2bfa3ef6e9725f7dc2345855..d7d218b025a0ff8834c5041ecf69eabe7ab6d44d 100644
--- a/Source/web/ServiceWorkerGlobalScopeClientImpl.cpp
+++ b/Source/web/ServiceWorkerGlobalScopeClientImpl.cpp
@@ -80,6 +80,11 @@ void ServiceWorkerGlobalScopeClientImpl::didHandleFetchEvent(int fetchEventID, P
 
     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);
 }