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

chrome/browser/ui/ash/launcher/browser_status_monitor.h

 // Copyright 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_BROWSER_UI_ASH_LAUNCHER_BROWSER_STATUS_MONITOR_H_
 #define CHROME_BROWSER_UI_ASH_LAUNCHER_BROWSER_STATUS_MONITOR_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 53 matching lines @@
 
   // TabStripModelObserver overrides:
   void ActiveTabChanged(content::WebContents* old_contents,
                         content::WebContents* new_contents,
                         int index,
                         int reason) override;
   void TabReplacedAt(TabStripModel* tab_strip_model,
                      content::WebContents* old_contents,
                      content::WebContents* new_contents,
                      int index) override;
-  void TabInsertedAt(content::WebContents* contents,
+  void TabInsertedAt(TabStripModel* tab_strip_model,
+                     content::WebContents* contents,
                      int index,
                      bool foreground) override;
   void TabClosingAt(TabStripModel* tab_strip_mode,
                     content::WebContents* contents,
                     int index) override;
 
   // Called from our own |LocalWebContentsObserver| when web contents did go
   // away without any other notification. This might happen in case of
   // application uninstalls, page crashes, ...).
   void WebContentsDestroyed(content::WebContents* web_contents);
@@ skipping 36 matching lines @@
   BrowserToAppIDMap browser_to_app_id_map_;
   WebContentsToObserverMap webcontents_to_observer_map_;
   std::unique_ptr<SettingsWindowObserver> settings_window_observer_;
 
   BrowserTabStripTracker browser_tab_strip_tracker_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserStatusMonitor);
 };
 
 #endif  // CHROME_BROWSER_UI_ASH_LAUNCHER_BROWSER_STATUS_MONITOR_H_