[NoStatePrefetch] Add UMA histogram to count prefetch requests

chrome/browser/prerender/prerender_resource_throttle.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_PRERENDER_PRERENDER_RESOURCE_THROTTLE_H_
 #define CHROME_BROWSER_PRERENDER_PRERENDER_RESOURCE_THROTTLE_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 19 matching lines @@
 class PrerenderResourceThrottle
     : public content::ResourceThrottle,
       public base::SupportsWeakPtr<PrerenderResourceThrottle> {
  public:
   explicit PrerenderResourceThrottle(net::URLRequest* request);
 
   // content::ResourceThrottle implementation:
   void WillStartRequest(bool* defer) override;
   void WillRedirectRequest(const net::RedirectInfo& redirect_info,
                            bool* defer) override;
+  void WillProcessResponse(bool* defer) override;
   const char* GetNameForLogging() const override;
 
   // Called by the PrerenderContents when a prerender becomes visible.
   // May only be called if currently throttling the resource.
   void Resume();
 
   static void OverridePrerenderContentsForTesting(PrerenderContents* contents);
 
  private:
   // Helper method to cancel the request. May only be called if currently
@@ skipping 10 matching lines @@
 
   static void WillRedirectRequestOnUI(
       const base::WeakPtr<PrerenderResourceThrottle>& throttle,
       const std::string& follow_only_when_prerender_shown_header,
       content::ResourceType resource_type,
       bool async,
       int render_process_id,
       int render_frame_id,
       const GURL& new_url);
 
+  static void WillProcessResponseOnUI(bool is_main_resource,
+                                      bool is_no_store,
+                                      int render_process_id,
+                                      int render_frame_id);
+
   // Helper to return the PrerenderContents given a render frame id. May return
   // NULL if it's gone.
   static PrerenderContents* PrerenderContentsFromRenderFrame(
       int render_process_id, int render_frame_id);
 
   net::URLRequest* request_;
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderResourceThrottle);
 };
 
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_RESOURCE_THROTTLE_H_