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

Source/core/timing/Performance.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2012 Intel 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.
@@ skipping 196 matching lines @@
 
     if (info.redirectChain().isEmpty()) {
         RefPtrWillBeRawPtr<PerformanceEntry> entry = PerformanceResourceTiming::create(info, initiatorDocument, startTime, allowTimingDetails);
         addResourceTimingBuffer(entry);
         return;
     }
 
     const Vector<ResourceResponse>& redirectChain = info.redirectChain();
     bool allowRedirectDetails = allowsTimingRedirect(redirectChain, finalResponse, initiatorDocument);
 
-    if (!allowRedirectDetails) {
+    // ServiceWorker doesn't support TimingInfo.
+    // FIXME: Implement ServiceWorkerURLRequestJob::GetLoadTimingInfo().
+    if (!allowRedirectDetails && !finalResponse.wasFetchedViaServiceWorker()) {
         ResourceLoadTiming* finalTiming = finalResponse.resourceLoadTiming();
         ASSERT(finalTiming);
         if (finalTiming)
             startTime = finalTiming->requestTime;
     }
 
     ResourceLoadTiming* lastRedirectTiming = redirectChain.last().resourceLoadTiming();
     ASSERT(lastRedirectTiming);
     double lastRedirectEndTime = lastRedirectTiming->receiveHeadersEnd;
 
@@ skipping 50 matching lines @@
 void Performance::trace(Visitor* visitor)
 {
     visitor->trace(m_navigation);
     visitor->trace(m_timing);
     visitor->trace(m_resourceTimingBuffer);
     visitor->trace(m_userTiming);
     EventTargetWithInlineData::trace(visitor);
 }
 
 } // namespace WebCore