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

chrome/browser/devtools/global_confirm_info_bar.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 CHROME_BROWSER_DEVTOOLS_GLOBAL_CONFIRM_INFO_BAR_H_
 #define CHROME_BROWSER_DEVTOOLS_GLOBAL_CONFIRM_INFO_BAR_H_
 
 #include <map>
 
 #include "base/macros.h"
@@ skipping 18 matching lines @@
       std::unique_ptr<ConfirmInfoBarDelegate> delegate);
   void Close();
 
  private:
   explicit GlobalConfirmInfoBar(
       std::unique_ptr<ConfirmInfoBarDelegate> delegate);
   ~GlobalConfirmInfoBar() override;
   class DelegateProxy;
 
   // TabStripModelObserver:
-  void TabInsertedAt(content::WebContents* web_contents,
+  void TabInsertedAt(TabStripModel* tab_strip_model,
+                     content::WebContents* web_contents,
                      int index,
                      bool foreground) override;
   void TabChangedAt(content::WebContents* web_contents,
                     int index,
                     TabChangeType change_type) override;
 
   // infobars::InfoBarManager::Observer:
   void OnInfoBarRemoved(infobars::InfoBar* info_bar, bool animate) override;
   void OnManagerShuttingDown(infobars::InfoBarManager* manager) override;
 
   std::unique_ptr<ConfirmInfoBarDelegate> delegate_;
   std::map<infobars::InfoBarManager*, DelegateProxy*> proxies_;
   BrowserTabStripTracker browser_tab_strip_tracker_;
 
   base::WeakPtrFactory<GlobalConfirmInfoBar> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GlobalConfirmInfoBar);
 };
 
 #endif  // CHROME_BROWSER_DEVTOOLS_GLOBAL_CONFIRM_INFO_BAR_H_