histogram synchronizer code between renderer and browser for UMA and about_histogram

chrome/renderer/render_thread.h

 // Copyright (c) 2006-2008 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_RENDER_THREAD_H_
 #define CHROME_RENDERER_RENDER_THREAD_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 79 matching lines @@
   UserScriptSlave* user_script_slave() const {
     return user_script_slave_.get();
   }
 
   bool plugin_refresh_allowed() const { return plugin_refresh_allowed_; }
 
   // Do DNS prefetch resolution of a hostname.
   void Resolve(const char* name, size_t length);
 
   // Send all the Histogram data to browser.
-  void SendHistograms();
+  void SendHistograms(int sequence_number);
 
   // Invokes InformHostOfCacheStats after a short delay.  Used to move this
   // bookkeeping operation off the critical latency path.
   void InformHostOfCacheStatsLater();
 
  private:
   virtual void OnControlMessageReceived(const IPC::Message& msg);
 
   // Called by the thread base class
   virtual void Init();
   virtual void CleanUp();
 
   void OnUpdateVisitedLinks(base::SharedMemoryHandle table);
   void OnUpdateUserScripts(base::SharedMemoryHandle table);
   void OnSetExtensionFunctionNames(const std::vector<std::string>& names);
   void OnSetNextPageID(int32 next_page_id);
   void OnCreateNewView(gfx::NativeViewId parent_hwnd,
                        ModalDialogEvent modal_dialog_event,
                        const WebPreferences& webkit_prefs,
                        int32 view_id);
   void OnTransferBitmap(const SkBitmap& bitmap, int resource_id);
   void OnSetCacheCapacities(size_t min_dead_capacity,
                             size_t max_dead_capacity,
                             size_t capacity);
   void OnGetCacheResourceStats();
 
   // Send all histograms to browser.
-  void OnGetRendererHistograms();
+  void OnGetRendererHistograms(int sequence_number);
 
   void OnExtensionHandleConnect(int channel_id, const std::string& tab_json);
   void OnExtensionHandleMessage(const std::string& message, int channel_id);
   void OnExtensionHandleEvent(const std::string event_name,
       const std::string event_data);
   void OnPurgePluginListCache();
 
   // Gather usage statistics from the in-memory cache and inform our host.
   // These functions should be call periodically so that the host can make
   // decisions about how to allocation resources using current information.
@@ skipping 21 matching lines @@
 
   scoped_refptr<DevToolsAgentFilter> devtools_agent_filter_;
 
   // If true, then a GetPlugins call is allowed to rescan the disk.
   bool plugin_refresh_allowed_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderThread);
 };
 
 #endif  // CHROME_RENDERER_RENDER_THREAD_H_