Bug 1191667 - Part 3. Call NotifyStartedPlaying to show audio indicator. r=eitan

dom/media/webspeech/synth/nsSpeechTask.cpp

@@ -667,6 +667,10 @@ nsSpeechTask::CreateAudioChannelAgent()
   mAudioChannelAgent->InitWithWeakCallback(mUtterance->GetOwner(),
                                            static_cast<int32_t>(AudioChannelService::GetDefaultAudioChannel()),
                                            this);
+  float volume = 0.0f;
+  bool muted = true;
+  mAudioChannelAgent->NotifyStartedPlaying(nsIAudioChannelAgent::AUDIO_AGENT_NOTIFY, &volume, &muted);
+  WindowVolumeChanged(volume, muted);
 }
 
 void