[Resource Timing] Memory cached resources should be reported on first use.

Source/core/timing/ResourceTimingInfo.h

 /*
  * Copyright (C) 2013 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.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 43 matching lines @@
 
     void setInitialRequest(const ResourceRequest& request) { m_initialRequest = request; }
     const ResourceRequest& initialRequest() const { return m_initialRequest; }
 
     void setFinalResponse(const ResourceResponse& response) { m_finalResponse = response; }
     const ResourceResponse& finalResponse() const { return m_finalResponse; }
 
     void addRedirect(const ResourceResponse& redirectResponse) { m_redirectChain.append(redirectResponse); }
     const Vector<ResourceResponse>& redirectChain() const { return m_redirectChain; }
 
+    void clearLoadTimings()
+    {
+        m_finalResponse.setResourceLoadTiming(0);
+        for (size_t i = 0; i < m_redirectChain.size(); ++i)
+            m_redirectChain[i].setResourceLoadTiming(0);
+    }
+
 private:
     ResourceTimingInfo(const AtomicString& type, const double time)
         : m_type(type)
         , m_initialTime(time)
     {
     }
 
     AtomicString m_type;
     double m_initialTime;
     double m_loadFinishTime;
     ResourceRequest m_initialRequest;
     ResourceResponse m_finalResponse;
     Vector<ResourceResponse> m_redirectChain;
 };
 
 } // namespace WebCore
 
 #endif