pass script fetch start / end time to Transalte Element to implement real time latency monitoring

components/translate/core/browser/translate_script.h

 // Copyright 2014 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 COMPONENTS_TRANSLATE_CORE_BROWSER_TRANSLATE_SCRIPT_H_
 #define COMPONENTS_TRANSLATE_CORE_BROWSER_TRANSLATE_SCRIPT_H_
 
 #include <memory>
 #include <string>
 #include <vector>
@@ skipping 62 matching lines @@
 
   // The callback when the script is fetched or a server error occured.
   void OnScriptFetchComplete(int id, bool success, const std::string& data);
 
   // URL fetcher to fetch the translate script.
   std::unique_ptr<TranslateURLFetcher> fetcher_;
 
   // The JS injected in the page to do the translation.
   std::string data_;
 
+  // The starting time of fetching the translate script.
+  // Number of milliseconds since the epoch.
+  double script_fetch_start_time_;
+
   // Delay after which the translate script is fetched again from the translate
   // server.
   base::TimeDelta expiration_delay_;
 
   // The callbacks called when the server sends a response.
   typedef std::vector<RequestCallback> RequestCallbackList;
   RequestCallbackList callback_list_;
 
   base::WeakPtrFactory<TranslateScript> weak_method_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TranslateScript);
 };
 
 }  // namespace translate
 
 #endif  // COMPONENTS_TRANSLATE_CORE_BROWSER_TRANSLATE_SCRIPT_H_