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

ash/system/date/tray_date.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 "ash/system/date/tray_date.h"
 
 #include "ash/shell.h"
 #include "ash/system/date/date_view.h"
 #include "ash/system/tray/system_tray_delegate.h"
 #include "ash/system/tray/tray_constants.h"
@@ skipping 55 matching lines @@
 void TrayDate::DestroyTrayView() {
   date_tray_.reset();
 }
 
 void TrayDate::DestroyDefaultView() {
 }
 
 void TrayDate::DestroyDetailedView() {
 }
 
+void TrayDate::UpdateAfterLoginStatusChange(user::LoginStatus status) {
+}
+
 void TrayDate::OnDateFormatChanged() {
   date_tray_->UpdateTimeFormat();
 }
 
 void TrayDate::Refresh() {
   date_tray_->UpdateText();
 }
 
 }  // namespace internal
 }  // namespace ash