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

chrome/browser/ui/tabs/tab_strip_model_observer.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_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 #define CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 
 class TabStripModel;
 
 namespace content {
@@ skipping 39 matching lines @@
     CHANGE_REASON_NONE = 0,
     // The active tab changed because the tab's web contents was replaced.
     CHANGE_REASON_REPLACED = 1 << 0,
     // The active tab changed due to a user input event.
     CHANGE_REASON_USER_GESTURE = 1 << 1,
   };
 
   // A new WebContents was inserted into the TabStripModel at the
   // specified index. |foreground| is whether or not it was opened in the
   // foreground (selected).
-  virtual void TabInsertedAt(content::WebContents* contents,
+  virtual void TabInsertedAt(TabStripModel* tab_strip_model,
+                             content::WebContents* contents,
                              int index,
                              bool foreground);
 
   // The specified WebContents at |index| is being closed (and eventually
   // destroyed). |tab_strip_model| is the TabStripModel that contained the tab.
   virtual void TabClosingAt(TabStripModel* tab_strip_model,
                             content::WebContents* contents,
                             int index);
 
   // The specified WebContents at |index| is being detached, perhaps to
@@ skipping 48 matching lines @@
 
   // The WebContents was replaced at the specified index. This is invoked
   // when instant is enabled and the user navigates by way of instant or when
   // prerendering swaps in a prerendered WebContents.
   virtual void TabReplacedAt(TabStripModel* tab_strip_model,
                              content::WebContents* old_contents,
                              content::WebContents* new_contents,
                              int index);
 
   // Invoked when the pinned state of a tab changes.
-  virtual void TabPinnedStateChanged(content::WebContents* contents, int index);
+  virtual void TabPinnedStateChanged(TabStripModel* tab_strip_model,
+                                     content::WebContents* contents,
+                                     int index);
 
   // Invoked when the blocked state of a tab changes.
   // NOTE: This is invoked when a tab becomes blocked/unblocked by a tab modal
   // window.
   virtual void TabBlockedStateChanged(content::WebContents* contents,
                                       int index);
 
   // The TabStripModel now no longer has any tabs. The implementer may
   // use this as a trigger to try and close the window containing the
   // TabStripModel, for example...
   virtual void TabStripEmpty();
 
   // Sent any time an attempt is made to close all the tabs. This is not
   // necessarily the result of CloseAllTabs(). For example, if the user closes
   // the last tab WillCloseAllTabs() is sent. If the close does not succeed
   // during the current event (say unload handlers block it) then
   // CloseAllTabsCanceled() is sent. Also note that if the last tab is detached
   // (DetachWebContentsAt()) then this is not sent.
   virtual void WillCloseAllTabs();
   virtual void CloseAllTabsCanceled();
 
  protected:
   virtual ~TabStripModelObserver() {}
 };
 
 #endif  // CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_