Add UMA to track time between preload discovery and reference

third_party/WebKit/Source/core/fetch/FetchRequest.h

 /*
  * Copyright (C) 2012 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 67 matching lines @@
 
     DeferOption defer() const { return m_defer; }
     void setDefer(DeferOption defer) { m_defer = defer; }
 
     ResourceWidth getResourceWidth() const { return m_resourceWidth; }
     void setResourceWidth(ResourceWidth);
 
     ClientHintsPreferences& clientHintsPreferences() { return m_clientHintPreferences; }
 
     bool forPreload() const { return m_forPreload; }
-    void setForPreload(bool forPreload) { m_forPreload = forPreload; }
+    void setForPreload(bool forPreload, double discoveryTime = 0)

[Yoav Weiss, 2016/05/31 18:36:18]

maybe move the implementation to the cpp file, as it's now more than a single
line? I don't think we have a strict rule for that, and if you really like to
keep it here, I can live with it, but I think it's better to keep the h files
lean and mean :)

[Charlie Harrison, 2016/05/31 19:06:06]

Done.

+    {
+        m_forPreload = forPreload;
+        m_preloadDiscoveryTime = discoveryTime;
+    }
+
+    double preloadDiscoveryTime() { return m_preloadDiscoveryTime; }
 
     bool isLinkPreload() { return m_linkPreload; }
     void setLinkPreload(bool isLinkPreload) { m_linkPreload = isLinkPreload; }
 
     void setContentSecurityCheck(ContentSecurityPolicyDisposition contentSecurityPolicyOption) { m_options.contentSecurityPolicyOption = contentSecurityPolicyOption; }
     void setCrossOriginAccessControl(SecurityOrigin*, CrossOriginAttributeValue);
     OriginRestriction getOriginRestriction() const { return m_originRestriction; }
     void setOriginRestriction(OriginRestriction restriction) { m_originRestriction = restriction; }
     const IntegrityMetadataSet& integrityMetadata() const { return m_integrityMetadata; }
     void setIntegrityMetadata(const IntegrityMetadataSet& metadata) { m_integrityMetadata = metadata; }
 
 private:
     ResourceRequest m_resourceRequest;
     String m_charset;
     ResourceLoaderOptions m_options;
     ResourceLoadPriority m_priority;
     bool m_forPreload;
     bool m_linkPreload;
+    double m_preloadDiscoveryTime;
     DeferOption m_defer;
     OriginRestriction m_originRestriction;
     ResourceWidth m_resourceWidth;
     ClientHintsPreferences m_clientHintPreferences;
     IntegrityMetadataSet m_integrityMetadata;
 };
 
 } // namespace blink
 
 #endif