mash: Move SystemTrayDelegate and dependencies to //ash/common

ash/volume_control_delegate.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_VOLUME_CONTROL_DELEGATE_H_
-#define ASH_VOLUME_CONTROL_DELEGATE_H_
-
-namespace ui {
-class Accelerator;
-}  // namespace ui
-
-namespace ash {
-
-// Delegate for controlling the volume.
-class VolumeControlDelegate {
- public:
-  virtual ~VolumeControlDelegate() {}
-
-  virtual void HandleVolumeMute(const ui::Accelerator& accelerator) = 0;
-  virtual void HandleVolumeDown(const ui::Accelerator& accelerator) = 0;
-  virtual void HandleVolumeUp(const ui::Accelerator& accelerator) = 0;
-};
-
-}  // namespace ash
-
-#endif  // ASH_VOLUME_CONTROL_DELEGATE_H_