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

chrome/browser/ui/tabs/tab_strip_model_unittest.cc

 // 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.
 
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 
 #include <stddef.h>
 
 #include <map>
 #include <memory>
@@ skipping 131 matching lines @@
       : tab_strip_model_(tab_strip_model) {
     tab_strip_model_->AddObserver(this);
   }
 
   ~TabBlockedStateTestBrowser() override {
     tab_strip_model_->RemoveObserver(this);
   }
 
  private:
   // TabStripModelObserver
-  void TabInsertedAt(WebContents* contents,
+  void TabInsertedAt(TabStripModel* tab_strip_model,
+                     WebContents* contents,
                      int index,
                      bool foreground) override {
     web_modal::WebContentsModalDialogManager* manager =
         web_modal::WebContentsModalDialogManager::FromWebContents(contents);
     if (manager)
       manager->SetDelegate(this);
   }
 
   // WebContentsModalDialogManagerDelegate
   void SetWebContentsBlocked(content::WebContents* contents,
@@ skipping 231 matching lines @@
     states_.push_back(State(contents, index, CHANGE));
   }
   void TabReplacedAt(TabStripModel* tab_strip_model,
                      WebContents* old_contents,
                      WebContents* new_contents,
                      int index) override {
     State s(new_contents, index, REPLACED);
     s.src_contents = old_contents;
     states_.push_back(s);
   }
-  void TabPinnedStateChanged(WebContents* contents, int index) override {
+  void TabPinnedStateChanged(TabStripModel* tab_strip_model,
+                             WebContents* contents,
+                             int index) override {
     states_.push_back(State(contents, index, PINNED));
   }
   void TabStripEmpty() override { empty_ = true; }
   void WillCloseAllTabs() override {
     states_.push_back(State(NULL, -1, CLOSE_ALL));
   }
   void CloseAllTabsCanceled() override {
     states_.push_back(State(NULL, -1, CLOSE_ALL_CANCELED));
   }
 
@@ skipping 2125 matching lines @@
   strip.AddObserver(&observer);
 
   strip.ActivateTabAt(1, true);
   EXPECT_EQ(1, strip.active_index());
 
   strip.MoveWebContentsAt(2, 3, true);
   EXPECT_EQ(3, strip.active_index());
 
   strip.CloseAllTabs();
 }