Refactor the TrayAudio code so that it can be used by other platforms.

ash/system/chromeos/audio/tray_audio_chromeos.h

Index: ash/system/chromeos/audio/tray_audio_chromeos.h
diff --git a/ash/system/chromeos/audio/tray_audio_chromeos.h b/ash/system/chromeos/audio/tray_audio_chromeos.h
new file mode 100644
index 0000000000000000000000000000000000000000..6817f856246c7f0484b193a81dbb9f17f54192a5
--- /dev/null
+++ b/ash/system/chromeos/audio/tray_audio_chromeos.h
@@ -0,0 +1,42 @@
+// 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_CHROMEOS_AUDIO_TRAY_AUDIO_CHROMEOS_H_
+#define ASH_SYSTEM_CHROMEOS_AUDIO_TRAY_AUDIO_CHROMEOS_H_
+
+#include "ash/ash_export.h"
+#include "ash/system/audio/tray_audio.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace ash {
+
+namespace internal {
+
+namespace tray {
+class AudioDetailedView;
+}
+
+class ASH_EXPORT TrayAudioChromeOs : public TrayAudio {
+ public:
+  explicit TrayAudioChromeOs(SystemTray* system_tray);
+  virtual ~TrayAudioChromeOs();
+
+ protected:
+  // Overridden from TrayAudio
+  virtual void Update() OVERRIDE;
+
+ private:
+  // Overridden from SystemTrayItem.
+  virtual views::View* CreateDetailedView(user::LoginStatus status) OVERRIDE;
+  virtual void DestroyDetailedView() OVERRIDE;
+
+  tray::AudioDetailedView* audio_detail_view_;
+
+  DISALLOW_COPY_AND_ASSIGN(TrayAudioChromeOs);
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_CHROMEOS_AUDIO_TRAY_AUDIO_CHROMEOS_H_