ash: Refresh the tray items, instead of recreating them, when login status changes.

ash/system/brightness/tray_brightness.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 ASH_SYSTEM_BRIGHTNESS_TRAY_BRIGHTNESS_H_
 #define ASH_SYSTEM_BRIGHTNESS_TRAY_BRIGHTNESS_H_
 #pragma once
 
 #include "ash/system/brightness/brightness_observer.h"
 #include "ash/system/tray/system_tray_item.h"
@@ skipping 23 matching lines @@
   // meantime.
   void HandleInitialBrightness(double percent);
 
   // Overridden from SystemTrayItem.
   virtual views::View* CreateTrayView(user::LoginStatus status) OVERRIDE;
   virtual views::View* CreateDefaultView(user::LoginStatus status) OVERRIDE;
   virtual views::View* CreateDetailedView(user::LoginStatus status) OVERRIDE;
   virtual void DestroyTrayView() OVERRIDE;
   virtual void DestroyDefaultView() OVERRIDE;
   virtual void DestroyDetailedView() OVERRIDE;
+  virtual void UpdateAfterLoginStatusChange(user::LoginStatus status) OVERRIDE;
 
   // Overridden from BrightnessObserver.
   virtual void OnBrightnessChanged(double percent,
                                    bool user_initiated) OVERRIDE;
 
   base::WeakPtrFactory<TrayBrightness> weak_ptr_factory_;
 
   scoped_ptr<tray::BrightnessView> brightness_view_;
 
   // Was |brightness_view_| created for CreateDefaultView() rather than
   // CreateDetailedView()?  Used to avoid resetting |brightness_view_|
   // inappropriately in DestroyDefaultView() or DestroyDetailedView().
   bool is_default_view_;
 
   // Brightness level in the range [0.0, 100.0] that we've heard about most
   // recently.
   double current_percent_;
 
   // Has |current_percent_| been initialized?
   bool got_current_percent_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayBrightness);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_BRIGHTNESS_TRAY_BRIGHTNESS_H_