Set up hdmi output device default volume to 100.

chrome/browser/chromeos/audio/audio_devices_pref_handler_impl.h

Index: chrome/browser/chromeos/audio/audio_devices_pref_handler_impl.h
diff --git a/chrome/browser/chromeos/audio/audio_devices_pref_handler_impl.h b/chrome/browser/chromeos/audio/audio_devices_pref_handler_impl.h
index 1a46dcfa303ef4b5bc01f47ed7b07d6473361f9d..e6ecdc779dd604ea1f293c7063f12affba75198f 100644
--- a/chrome/browser/chromeos/audio/audio_devices_pref_handler_impl.h
+++ b/chrome/browser/chromeos/audio/audio_devices_pref_handler_impl.h
@@ -22,7 +22,8 @@ class AudioDevicesPrefHandlerImpl : public AudioDevicesPrefHandler {
   explicit AudioDevicesPrefHandlerImpl(PrefService* local_state);
 
   // Overridden from AudioDevicesPrefHandler.
-  virtual double GetVolumeGainValue(const AudioDevice& device) OVERRIDE;
+  virtual double GetOutputVolumeValue(const AudioDevice* device) OVERRIDE;
+  virtual double GetInputGainValue(const AudioDevice* device) OVERRIDE;
   virtual void SetVolumeGainValue(const AudioDevice& device,
                                   double value) OVERRIDE;
 
@@ -53,6 +54,9 @@ class AudioDevicesPrefHandlerImpl : public AudioDevicesPrefHandler {
   void UpdateDevicesVolumePref();
   void SaveDevicesVolumePref();
 
+  double GetVolumeGainPrefValue(const AudioDevice& device);
+  double GetDeviceDefaultOutputVolume(const AudioDevice& device);
+
   // Methods to migrate the mute and volume settings for a device from the
   // previous global pref value to the new per device pref value for the
   // current active device. If a previous global setting doesn't exist, we'll