mash: Migrate tray audio and deps to common.

ash/common/system/audio/audio_observer.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_AUDIO_OBSERVER_H_
-#define ASH_SYSTEM_AUDIO_AUDIO_OBSERVER_H_
+#ifndef ASH_COMMON_SYSTEM_AUDIO_AUDIO_OBSERVER_H_
+#define ASH_COMMON_SYSTEM_AUDIO_AUDIO_OBSERVER_H_
 
 #include <stdint.h>
 
 namespace ash {
 
 class AudioObserver {
  public:
   virtual ~AudioObserver() {}
 
   // Called when an active output device's volume changed.
@@ skipping 14 matching lines @@
 
   // Called when active audio output node changed.
   virtual void OnActiveOutputNodeChanged() = 0;
 
   // Called when active audio input node changed.
   virtual void OnActiveInputNodeChanged() = 0;
 };
 
 }  // namespace ash
 
-#endif  // ASH_SYSTEM_AUDIO_AUDIO_OBSERVER_H_
+#endif  // ASH_COMMON_SYSTEM_AUDIO_AUDIO_OBSERVER_H_