Remove non-MD code from AudioDetailedView

ash/common/system/chromeos/audio/volume_view.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_COMMON_SYSTEM_CHROMEOS_AUDIO_VOLUME_VIEW_H_
 #define ASH_COMMON_SYSTEM_CHROMEOS_AUDIO_VOLUME_VIEW_H_
 
 #include "base/macros.h"
 #include "ui/views/controls/button/button.h"
 #include "ui/views/controls/slider.h"
 #include "ui/views/view.h"
 
 namespace views {
 class CustomButton;
 class ImageView;
-class Slider;
 }
 
 namespace ash {
 class SystemTrayItem;
 class TriView;
 
 namespace system {
 class TrayAudioDelegate;
 }
 
@@ skipping 41 matching lines @@
   views::ImageView* device_type_;
   bool is_default_view_;
 
   DISALLOW_COPY_AND_ASSIGN(VolumeView);
 };
 
 }  // namespace tray
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_CHROMEOS_AUDIO_VOLUME_VIEW_H_