Revert of Enable the volume slider in Ash for windows.

ash/system/win/audio/tray_audio_win.h

-// Copyright 2014 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_WIN_AUDIO_TRAY_AUDIO_WIN_H_
-#define ASH_SYSTEM_WIN_AUDIO_TRAY_AUDIO_WIN_H_
-
-#include "ash/ash_export.h"
-#include "ash/system/audio/tray_audio.h"
-#include "base/memory/scoped_ptr.h"
-
-namespace ash {
-
-namespace internal {
-
-class TrayAudioWin : public TrayAudio {
- public:
-  explicit TrayAudioWin(SystemTray* system_tray);
-  virtual ~TrayAudioWin();
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(TrayAudioWin);
-};
-
-}  // namespace internal
-}  // namespace ash
-
-#endif  // ASH_SYSTEM_WIN_AUDIO_TRAY_AUDIO_WIN_H_