Use PrefChangeRegistrar everywhere

chrome/browser/background_mode_manager.h

 // Copyright (c) 2010 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_BACKGROUND_MODE_MANAGER_H_
 #define CHROME_BROWSER_BACKGROUND_MODE_MANAGER_H_
 #pragma once
 
 #include "app/menus/simple_menu_model.h"
 #include "base/gtest_prod_util.h"
+#include "chrome/browser/prefs/pref_change_registrar.h"
 #include "chrome/browser/status_icons/status_icon.h"
 #include "chrome/common/notification_observer.h"
 #include "chrome/common/notification_registrar.h"
 
 class Browser;
 class Extension;
 class PrefService;
 class Profile;
 class StatusIcon;
 class StatusTray;
@@ skipping 114 matching lines @@
   // user disables/enables background mode via preferences.
   bool in_background_mode_;
 
   // Reference to our status tray (owned by our parent profile). If null, the
   // platform doesn't support status icons.
   StatusTray* status_tray_;
 
   // Reference to our status icon (if any) - owned by the StatusTray.
   StatusIcon* status_icon_;
 
+  // Ensure observed preferences are properly cleaned up.
+  PrefChangeRegistrar pref_registrar_;
+
   DISALLOW_COPY_AND_ASSIGN(BackgroundModeManager);
 };
 
 #endif  // CHROME_BROWSER_BACKGROUND_MODE_MANAGER_H_