Update {virtual,override,final} to follow C++11 style in ui.

ui/chromeos/user_activity_power_manager_notifier.h

 // Copyright 2014 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 UI_CHROMEOS_USER_ACTIVITY_POWER_MANAGER_NOTIFIER_H_
 #define UI_CHROMEOS_USER_ACTIVITY_POWER_MANAGER_NOTIFIER_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/time/time.h"
 #include "ui/base/user_activity/user_activity_observer.h"
 #include "ui/chromeos/ui_chromeos_export.h"
 
 namespace ui {
 
 class UserActivityDetector;
 
 // Notifies the power manager when the user is active.
 class UI_CHROMEOS_EXPORT UserActivityPowerManagerNotifier
     : public UserActivityObserver {
  public:
   explicit UserActivityPowerManagerNotifier(UserActivityDetector* detector);
-  virtual ~UserActivityPowerManagerNotifier();
+  ~UserActivityPowerManagerNotifier() override;
 
   // UserActivityObserver implementation.
-  virtual void OnUserActivity(const Event* event) override;
+  void OnUserActivity(const Event* event) override;
 
  private:
   UserActivityDetector* detector_;  // not owned
 
   // Last time that the power manager was notified.
   base::TimeTicks last_notify_time_;
 
   DISALLOW_COPY_AND_ASSIGN(UserActivityPowerManagerNotifier);
 };
 
 }  // namespace ui
 
 #endif  // UI_CHROMEOS_USER_ACTIVITY_POWER_MANAGER_NOTIFIER_H_