Introduce TabStripModelStatsRecorder class to record tab interaction stats

chrome/browser/ui/uma_browsing_activity_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_UMA_BROWSING_ACTIVITY_OBSERVER_H_
 #define CHROME_BROWSER_UI_UMA_BROWSING_ACTIVITY_OBSERVER_H_
 
+#include "chrome/browser/ui/tabs/tab_strip_model_stats_recorder.h"
+#include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
-#include "content/public/browser/notification_observer.h"
 
 namespace chrome {
 
 // This object is instantiated when the first Browser object is added to the
 // list and delete when the last one is removed. It watches for loads and
 // creates histograms of some global object counts.
 class UMABrowsingActivityObserver : public content::NotificationObserver {
  public:
   static void Init();
 
  private:
   UMABrowsingActivityObserver();
   ~UMABrowsingActivityObserver() override;
 
   // content::NotificationObserver implementation.
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
   // Counts the number of active RenderProcessHosts and logs them.
   void LogRenderProcessHostCount() const;
 
   // Counts the number of tabs in each browser window and logs them. This is
   // different than the number of WebContents objects since WebContents objects
   // can be used for popups and in dialog boxes. We're just counting toplevel
   // tabs here.
   void LogBrowserTabCount() const;
 
   content::NotificationRegistrar registrar_;
+  TabStripModelStatsRecorder tab_recorder_;
 
   DISALLOW_COPY_AND_ASSIGN(UMABrowsingActivityObserver);
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_UMA_BROWSING_ACTIVITY_OBSERVER_H_