Enable the volume slider in Ash for windows.

ash/system/win/audio/tray_audio_delegate_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_AUDIO_TRAY_AUDIO_DELEGATE_CHROMEOS_H_
-#define ASH_SYSTEM_AUDIO_TRAY_AUDIO_DELEGATE_CHROMEOS_H_
+#ifndef ASH_SYSTEM_WIN_AUDIO_TRAY_AUDIO_DELEGATE_WIN_H_
+#define ASH_SYSTEM_WIN_AUDIO_TRAY_AUDIO_DELEGATE_WIN_H_
+
+#include <audioclient.h>
+#include <mmdeviceapi.h>
 
 #include "ash/ash_export.h"
 #include "ash/system/audio/tray_audio_delegate.h"
 #include "base/compiler_specific.h"
+#include "base/win/scoped_comptr.h"
 
 namespace ash {
 namespace system {
 
-class ASH_EXPORT TrayAudioDelegateChromeOs : public TrayAudioDelegate {
+class ASH_EXPORT TrayAudioDelegateWin : public TrayAudioDelegate {
  public:
-  virtual ~TrayAudioDelegateChromeOs() {}
+  virtual ~TrayAudioDelegateWin() {}
 
   // Overridden from TrayAudioDelegate.
   virtual void AdjustOutputVolumeToAudibleLevel() OVERRIDE;
   virtual int GetOutputDefaultVolumeMuteLevel() OVERRIDE;
   virtual int GetOutputVolumeLevel() OVERRIDE;
   virtual int GetActiveOutputDeviceIconId() OVERRIDE;
   virtual bool HasAlternativeSources() OVERRIDE;
   virtual bool IsOutputAudioMuted() OVERRIDE;
   virtual void SetOutputAudioIsMuted(bool is_muted) OVERRIDE;
   virtual void SetOutputVolumeLevel(int level) OVERRIDE;
+
+ private:
+  base::win::ScopedComPtr<ISimpleAudioVolume> CreateDefaultVolumeControl();
 };
 
 }  // namespace system
 }  // namespace ash
 
-#endif  // ASH_SYSTEM_AUDIO_TRAY_AUDIO_DELEGATE_CHROMEOS_H_
+#endif  // ASH_SYSTEM_WIN_AUDIO_TRAY_AUDIO_DELEGATE_WIN_H_