Add metrics to keep track of the tab activate/deactivate cycle

chrome/browser/ui/browser_command_controller.h

 // Copyright (c) 2012 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_UI_BROWSER_COMMAND_CONTROLLER_H_
 #define CHROME_BROWSER_UI_BROWSER_COMMAND_CONTROLLER_H_
 
 #include <vector>
 
 #include "base/macros.h"
@@ skipping 66 matching lines @@
       Profile* profile);
 
  private:
   class InterstitialObserver;
 
   // Overridden from CommandUpdaterDelegate:
   void ExecuteCommandWithDisposition(int id, WindowOpenDisposition disposition)
       override;
 
   // Overridden from TabStripModelObserver:
-  void TabInsertedAt(content::WebContents* contents,
+  void TabInsertedAt(TabStripModel* tab_strip_model,
+                     content::WebContents* contents,
                      int index,
                      bool foreground) override;
   void TabDetachedAt(content::WebContents* contents, int index) override;
   void TabReplacedAt(TabStripModel* tab_strip_model,
                      content::WebContents* old_contents,
                      content::WebContents* new_contents,
                      int index) override;
   void TabBlockedStateChanged(content::WebContents* contents,
                               int index) override;
 
@@ skipping 93 matching lines @@
   PrefChangeRegistrar profile_pref_registrar_;
   PrefChangeRegistrar local_pref_registrar_;
   BooleanPrefMember pref_signin_allowed_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserCommandController);
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_BROWSER_COMMAND_CONTROLLER_H_