[Night Light] CL2: Ash and system tray work

ash/system/tiles/tiles_default_view.h

 // Copyright 2016 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_TILES_TILES_DEFAULT_VIEW_H_
 #define ASH_SYSTEM_TILES_TILES_DEFAULT_VIEW_H_
 
 #include "ash/ash_export.h"
 #include "base/macros.h"
 #include "ui/views/controls/button/button.h"
@@ skipping 30 matching lines @@
  private:
   friend class TrayTilesTest;
 
   SystemTrayItem* owner_;
 
   // Pointers to the child buttons of |this|. Note that some buttons may not
   // exist (depending on the user's current login status, for instance), in
   // which case the corresponding pointer will be null.
   views::CustomButton* settings_button_;
   views::CustomButton* help_button_;
+  views::CustomButton* night_light_button_;
   views::CustomButton* lock_button_;
   views::CustomButton* power_button_;
 
   DISALLOW_COPY_AND_ASSIGN(TilesDefaultView);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TILES_TILES_DEFAULT_VIEW_H_