chromeos: Combine TrayAudio and TrayAudioChromeOs classes

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_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.
-  // |node_id|: id of the active node.
-  // |volume|: volume as a percentage, 0.0 -- 100.0.
-  virtual void OnOutputNodeVolumeChanged(uint64_t node_id, double volume) = 0;
-
-  // Called when output mute state changed.
-  // |mute_on|: True if output is muted.
-  // |system_adjust|: True if the mute state is adjusted by the system
-  // automatically, UI should be consistent with the system's mute state,
-  // but it should not be too loud, e.g., the volume pop up window should not
-  // be triggered.
-  virtual void OnOutputMuteChanged(bool mute_on, bool system_adjust) = 0;
-
-  // Called when audio nodes changed.
-  virtual void OnAudioNodesChanged() = 0;
-
-  // 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_COMMON_SYSTEM_AUDIO_AUDIO_OBSERVER_H_