Add a new audio extension event OnLevelChanged.

extensions/browser/api/audio/audio_api.cc

Index: extensions/browser/api/audio/audio_api.cc
diff --git a/extensions/browser/api/audio/audio_api.cc b/extensions/browser/api/audio/audio_api.cc
index 659ae6ce67637ac20228a53e47681c1ab558b37a..3bd7219067503c3a6443614a10f6cca1549530f5 100644
--- a/extensions/browser/api/audio/audio_api.cc
+++ b/extensions/browser/api/audio/audio_api.cc
@@ -45,6 +45,16 @@ void AudioAPI::OnDeviceChanged() {
   }
 }
 
+void AudioAPI::OnOutputNodeVolumeChanged(const std::string& id, double volume) {
+  if (browser_context_ && EventRouter::Get(browser_context_)) {
+    scoped_ptr<base::ListValue> args =
+        audio::OnOutputNodeVolumeChanged::Create(id, volume);
+    scoped_ptr<Event> event(
+        new Event(audio::OnOutputNodeVolumeChanged::kEventName, args.Pass()));
+    EventRouter::Get(browser_context_)->BroadcastEvent(event.Pass());
+  }
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 bool AudioGetInfoFunction::RunAsync() {
@@ -107,4 +117,27 @@ bool AudioSetPropertiesFunction::RunSync() {
     return true;
 }
 
+///////////////////////////////////////////////////////////////////////////////
+
+bool AudioGetDeviceInfoFunction::RunAsync() {
+  AudioService* service =
+      AudioAPI::GetFactoryInstance()->Get(browser_context())->GetService();
+  DCHECK(service);
+  service->StartGetDeviceInfo(
+      base::Bind(&AudioGetDeviceInfoFunction::OnGetDeviceInfoCompleted, this));
+  return true;
+}
+
+void AudioGetDeviceInfoFunction::OnGetDeviceInfoCompleted(
+    const DevicesInfo& devices_info,
+    bool success) {
+  if (success)
+    results_ = audio::GetDeviceInfo::Results::Create(devices_info);
+  else
+    SetError("Error occurred when querying audio device information.");
+  SendResponse(success);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
 }  // namespace extensions