mash: Move SystemTrayImage and TrayImageItem to //ash/common

ash/system/tray/tray_empty.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_TRAY_TRAY_EMPTY_H_
 #define ASH_SYSTEM_TRAY_TRAY_EMPTY_H_
 
-#include "ash/system/tray/system_tray_item.h"
+#include "ash/common/system/tray/system_tray_item.h"
 #include "base/macros.h"
 
 namespace ash {
 
 class TrayEmpty : public SystemTrayItem {
  public:
   explicit TrayEmpty(SystemTray* system_tray);
   ~TrayEmpty() override;
 
  private:
   // Overridden from SystemTrayItem.
   views::View* CreateTrayView(LoginStatus status) override;
   views::View* CreateDefaultView(LoginStatus status) override;
   views::View* CreateDetailedView(LoginStatus status) override;
   void DestroyTrayView() override;
   void DestroyDefaultView() override;
   void DestroyDetailedView() override;
   void UpdateAfterLoginStatusChange(LoginStatus status) override;
 
   DISALLOW_COPY_AND_ASSIGN(TrayEmpty);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_TRAY_EMPTY_H_