Fix the volume controlling behaviors.

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_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/observer_list.h"
@@ skipping 15 matching lines @@
     virtual void OnVolumeChanged() = 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
+  // ownership of |mixer|.
+  static void InitializeForTesting(AudioMixer* mixer);
+
   // GetInstance returns NULL if not initialized or if already shutdown.
   static AudioHandler* GetInstance();
 
   // Registers volume and mute preferences.
   static void RegisterPrefs(PrefService* local_state);
 
   // Gets volume level in our internal 0-100% range, 0 being pure silence.
   double GetVolumePercent();
 
   // Sets volume level from 0-100%.
   void SetVolumePercent(double volume_percent);
 
   // Adjusts volume up (positive percentage) or down (negative percentage).
   void AdjustVolumeByPercent(double adjust_by_percent);
 
   // Is the volume currently muted?
   bool IsMuted();
 
   // Mutes or unmutes all audio.
   void SetMuted(bool do_mute);
 
   void AddVolumeObserver(VolumeObserver* observer);
   void RemoveVolumeObserver(VolumeObserver* observer);
 
  private:
   // Defines the delete on exit Singleton traits we like.  Best to have this
   // and constructor/destructor private as recommended for Singletons.
   friend struct DefaultSingletonTraits<AudioHandler>;
 
-  AudioHandler();
+  // Takes ownership of |mixer|.
+  explicit AudioHandler(AudioMixer* mixer);
   virtual ~AudioHandler();
 
   scoped_ptr<AudioMixer> mixer_;
 
   ObserverList<VolumeObserver> volume_observers_;
 
   PrefService* prefs_;  // not owned
 
   DISALLOW_COPY_AND_ASSIGN(AudioHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_AUDIO_AUDIO_HANDLER_H_