Implement new audio handler which talks to the new audio dbus apis.

chromeos/audio/audio_pref_observer.h

+// Copyright (c) 2013 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 CHROMEOS_AUDIO_AUDIO_PREF_OBSERVER_H_
+#define CHROMEOS_AUDIO_AUDIO_PREF_OBSERVER_H_
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "chromeos/chromeos_export.h"
+
+class PrefRegistrySimple;
+
+namespace chromeos {
+
+// Interface for observing audio preference changes.
+class CHROMEOS_EXPORT AudioPrefObserver {
+ public:
+  // Called when audio policy prefs changed.
+  virtual void OnAudioPolicyPrefChanged() = 0;
+
+ protected:
+  virtual ~AudioPrefObserver() {}
+};
+
+}  // namespace chromeos
+
+#endif  // CHROMEOS_AUDIO_AUDIO_PREF_OBSERVER_H_