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

chrome/browser/ui/views/ash/tab_scrubber_browsertest.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/views/ash/tab_scrubber.h"
 
 #include <memory>
 
 #include "ash/display/event_transformation_handler.h"
 #include "ash/shell.h"
@@ skipping 180 matching lines @@
     TabStrip* tab_strip = GetTabStrip(browser);
     for (int i = 0; i < num_tabs; ++i)
       AddBlankTabAndShow(browser);
     ASSERT_EQ(num_tabs + 1, browser->tab_strip_model()->count());
     ASSERT_EQ(num_tabs, browser->tab_strip_model()->active_index());
     tab_strip->StopAnimating(true);
     ASSERT_FALSE(tab_strip->IsAnimating());
   }
 
   // TabStripModelObserver overrides.
-  void TabInsertedAt(content::WebContents* contents,

[Patrick Monette, 2016/09/16 00:14:01]

Cleaned up this code while I was here.

An empty implementation of all function already exists in
TabStripModelObserver.

-                     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 {
     activation_order_.push_back(index);
     if (index == target_index_)
       quit_closure_.Run();
   }
 
-  void TabSelectionChanged(TabStripModel* tab_strip_model,
-                           const ui::ListSelectionModel& old_model) override {}
-  void TabMoved(content::WebContents* contents,
-                int from_index,
-                int to_index) override {}
-  void TabChangedAt(content::WebContents* contents,
-                    int index,
-                    TabChangeType change_type) override {}
-  void TabReplacedAt(TabStripModel* tab_strip_model,
-                     content::WebContents* old_contents,
-                     content::WebContents* new_contents,
-                     int index) override {}
-  void TabPinnedStateChanged(content::WebContents* contents,
-                             int index) override {}
-  void TabBlockedStateChanged(content::WebContents* contents,
-                              int index) override {}
-  void TabStripEmpty() override {}
-
   // History of tab activation. Scrub() resets it.
   std::vector<int> activation_order_;
 
  private:
   void RunUntilTabActive(Browser* browser, int target) {
     base::RunLoop run_loop;
     quit_closure_ = content::GetQuitTaskForRunLoop(&run_loop);
     browser->tab_strip_model()->AddObserver(this);
     target_index_ = target;
     content::RunThisRunLoop(&run_loop);
@@ skipping 248 matching lines @@
 
   SendScrubEvent(browser(), 1);
   EXPECT_TRUE(TabScrubber::GetInstance()->IsActivationPending());
   browser()->tab_strip_model()->ToggleSelectionAt(0);
   browser()->tab_strip_model()->ToggleSelectionAt(2);
   browser()->tab_strip_model()->MoveSelectedTabsTo(2);
   EXPECT_EQ(0, TabScrubber::GetInstance()->highlighted_tab());
 }
 
 #endif  // defined(OS_CHROMEOS)