Implement new slider control and disable the volume control when audio is muted.

chrome/browser/chromeos/audio/audio_handler.h

 // Copyright (c) 2012 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 CHROME_BROWSER_CHROMEOS_AUDIO_AUDIO_HANDLER_H_
 #define CHROME_BROWSER_CHROMEOS_AUDIO_AUDIO_HANDLER_H_
 
 #include "base/basictypes.h"
 #include "base/observer_list.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/thread.h"
 
 template <typename T> struct DefaultSingletonTraits;
 
 class PrefService;
 
 namespace chromeos {
 
 class AudioMixer;
 
 class AudioHandler {
  public:
   class VolumeObserver {
    public:
     virtual void OnVolumeChanged() = 0;
+    virtual void OnMuteToggled() = 0;
    protected:
     VolumeObserver() {}
     virtual ~VolumeObserver() {}
     DISALLOW_COPY_AND_ASSIGN(VolumeObserver);
   };
 
   static void Initialize();
   static void Shutdown();
 
   // Same as Initialize but using the specified audio mixer.  It takes
@@ skipping 38 matching lines @@
   ObserverList<VolumeObserver> volume_observers_;
 
   PrefService* prefs_;  // not owned
 
   DISALLOW_COPY_AND_ASSIGN(AudioHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_AUDIO_AUDIO_HANDLER_H_