text: // Copyright (c) 2013 The Chromium OS 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 POWER_MANAGER_POWERD_SYSTEM_AUDIO_OBSERVER_H_
  #define POWER_MANAGER_POWERD_SYSTEM_AUDIO_OBSERVER_H_
  
  #include <base/observer_list_types.h>
  
  namespace power_manager {
  namespace system {
  
  // Interface for classes interested in observing audio activity detected by
  // the AudioDetector class.
  class AudioObserver : public base::CheckedObserver {
   public:
    virtual ~AudioObserver() {}
  
    // Called when audio activity starts or stops.
    virtual void OnAudioStateChange(bool active) = 0;
  };
  
  }  // namespace system
  }  // namespace power_manager
  
  #endif  // POWER_MANAGER_POWERD_SYSTEM_AUDIO_OBSERVER_H_
  