[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 e6dc236f805a352f399f5aafa0cdd1f53d505ea6..0e644187def55602aa67eb4ae8ced486fff7e2ca 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);
 }