Split PrefService into PrefService, PrefServiceSimple and PrefServiceSyncable.

chrome/browser/chromeos/audio/audio_handler.h

Index: chrome/browser/chromeos/audio/audio_handler.h
diff --git a/chrome/browser/chromeos/audio/audio_handler.h b/chrome/browser/chromeos/audio/audio_handler.h
index 870d3c3071eb8c97c3a62efb685144266b7ba013..78b333ba6d9915984c3a3688854c038aae4e6304 100644
--- a/chrome/browser/chromeos/audio/audio_handler.h
+++ b/chrome/browser/chromeos/audio/audio_handler.h
@@ -15,6 +15,7 @@ template <typename T> struct DefaultSingletonTraits;
 
 class PrefChangeRegistrar;
 class PrefService;
+class PrefServiceSimple;
 
 namespace chromeos {
 
@@ -43,7 +44,7 @@ class AudioHandler {
   static AudioHandler* GetInstance();
 
   // Registers volume and mute preferences.
-  static void RegisterPrefs(PrefService* local_state);
+  static void RegisterPrefs(PrefServiceSimple* local_state);
 
   // Gets volume level in our internal 0-100% range, 0 being pure silence.
   double GetVolumePercent();