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

chrome/common/localized_error.h

 // Copyright (c) 2011 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_COMMON_LOCALIZED_ERROR_H_
 #define CHROME_COMMON_LOCALIZED_ERROR_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 33 matching lines @@
                                         bool is_post);
 
   // Returns true if an error page exists for the specified parameters.
   static bool HasStrings(const std::string& error_domain, int error_code);
 
   static const char kHttpErrorDomain[];
 
  private:
   // Sets up the Google Cached Copy button experiment if part of the
   // field trial. This promotes the Google cached copy suggestion from under
-  // the details section to a blue button.
+  // the details section to a blue button. Also experiments with the
+  // button label.
   static void EnableGoogleCachedCopyButtonExperiment(
       base::ListValue* suggestions,
       base::DictionaryValue* error_strings);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(LocalizedError);
 };
 
 #endif  // CHROME_COMMON_LOCALIZED_ERROR_H_