Adding ArcBridge Interface for Volume Update Requests

components/arc/audio/arc_audio_bridge.cc

Index: components/arc/audio/arc_audio_bridge.cc
diff --git a/components/arc/audio/arc_audio_bridge.cc b/components/arc/audio/arc_audio_bridge.cc
index 9a0da08829a5e88cb2ac299b71b027dd542637fd..a3eb2719f21404eb3d926b07b8738c685de5025b 100644
--- a/components/arc/audio/arc_audio_bridge.cc
+++ b/components/arc/audio/arc_audio_bridge.cc
@@ -39,6 +39,16 @@ void ArcAudioBridge::ShowVolumeControls() {
   ash::TrayAudio::ShowPopUpVolumeView();
 }
 
+void ArcAudioBridge::OnSystemVolumeUpdateRequest(int32_t percent) {
+  if (percent < 0 || percent > 100)
+    return;
+  cras_audio_handler_->SetOutputVolumePercent(percent);
+  bool is_muted =
+      percent <= cras_audio_handler_->GetOutputDefaultVolumeMuteThreshold();

[dcheng, 2017/06/06 18:45:38]

FWIW, it seems like this is already down in CrasAudioHandler:
https://cs.chromium.org/chromium/src/chromeos/audio/cras_audio_handler.cc?rcl...

[yueli, 2017/06/06 20:01:40]

IIUC SetOutputMute will change the device mute settings, which is not equivalent
to set volume to 0.

+  if (cras_audio_handler_->IsOutputMuted() != is_muted)
+    cras_audio_handler_->SetOutputMute(is_muted);
+}
+
 void ArcAudioBridge::OnAudioNodesChanged() {
   uint64_t output_id = cras_audio_handler_->GetPrimaryActiveOutputNode();
   const chromeos::AudioDevice* output_device =