Add UMA histograms for Google cached copy experiment on network error interstitial

chrome/renderer/net/net_error_helper.h

 // Copyright (c) 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_RENDERER_NET_NET_ERROR_HELPER_H_
 #define CHROME_RENDERER_NET_NET_ERROR_HELPER_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 71 matching lines @@
   void TrackClick(int tracking_id);
 
  private:
   // NetErrorHelperCore::Delegate implementation:
   void GenerateLocalizedErrorPage(
       const blink::WebURLError& error,
       bool is_failed_post,
       scoped_ptr<error_page::ErrorPageParams> params,
       bool* reload_button_shown,
       bool* show_saved_copy_button_shown,
+      bool* show_cached_copy_button_shown,
+      bool* show_cached_page_button_shown,
       std::string* html) const override;
   void LoadErrorPageInMainFrame(const std::string& html,
                                 const GURL& failed_url) override;
   void EnablePageHelperFunctions() override;
   void UpdateErrorPage(const blink::WebURLError& error,
                        bool is_failed_post) override;
   void FetchNavigationCorrections(
       const GURL& navigation_correction_url,
       const std::string& navigation_correction_request_body) override;
   void CancelFetchNavigationCorrections() override;
@@ skipping 17 matching lines @@
 
   scoped_ptr<content::ResourceFetcher> correction_fetcher_;
   scoped_ptr<content::ResourceFetcher> tracking_fetcher_;
 
   scoped_ptr<error_page::NetErrorHelperCore> core_;
 
   DISALLOW_COPY_AND_ASSIGN(NetErrorHelper);
 };
 
 #endif  // CHROME_RENDERER_NET_NET_ERROR_HELPER_H_