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

chrome/browser/ui/browser.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_H_
 #define CHROME_BROWSER_UI_BROWSER_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 410 matching lines @@
   // when it is removed from it.
   void RegisterKeepAlive();
   void UnregisterKeepAlive();
 
   // Interface implementations ////////////////////////////////////////////////
 
   // Overridden from content::PageNavigator:
   content::WebContents* OpenURL(const content::OpenURLParams& params) override;
 
   // Overridden from TabStripModelObserver:
-  void TabInsertedAt(content::WebContents* contents,
+  void TabInsertedAt(TabStripModel* tab_strip_model,
+                     content::WebContents* contents,
                      int index,
                      bool foreground) override;
   void TabClosingAt(TabStripModel* tab_strip_model,
                     content::WebContents* contents,
                     int index) override;
   void TabDetachedAt(content::WebContents* contents, int index) override;
   void TabDeactivated(content::WebContents* contents) override;
   void ActiveTabChanged(content::WebContents* old_contents,
                         content::WebContents* new_contents,
                         int index,
                         int reason) override;
   void TabMoved(content::WebContents* contents,
                 int from_index,
                 int to_index) override;
   void TabReplacedAt(TabStripModel* tab_strip_model,
                      content::WebContents* old_contents,
                      content::WebContents* new_contents,
                      int index) override;
-  void TabPinnedStateChanged(content::WebContents* contents,
+  void TabPinnedStateChanged(TabStripModel* tab_strip_model,
+                             content::WebContents* contents,
                              int index) override;
   void TabStripEmpty() override;
 
   // Overridden from content::WebContentsDelegate:
   bool CanOverscrollContent() const override;
   bool ShouldPreserveAbortedURLs(content::WebContents* source) override;
   void SetFocusToLocationBar(bool select_all) override;
   bool PreHandleKeyboardEvent(content::WebContents* source,
                               const content::NativeWebKeyboardEvent& event,
                               bool* is_keyboard_shortcut) override;
@@ skipping 541 matching lines @@
   // The following factory is used for chrome update coalescing.
   base::WeakPtrFactory<Browser> chrome_updater_factory_;
 
   // The following factory is used to close the frame at a later time.
   base::WeakPtrFactory<Browser> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Browser);
 };
 
 #endif  // CHROME_BROWSER_UI_BROWSER_H_