Reland "Avoid hitting the thread check when WebRtcAudioRenderer is going away"

content/renderer/media/media_stream_audio_processor.cc

Index: content/renderer/media/media_stream_audio_processor.cc
diff --git a/content/renderer/media/media_stream_audio_processor.cc b/content/renderer/media/media_stream_audio_processor.cc
index 074089ab69b506ed051f5262bed4a4dd6a52ddd2..4c1a2c90ab299c27846cebd1c56e730cc9f0f22a 100644
--- a/content/renderer/media/media_stream_audio_processor.cc
+++ b/content/renderer/media/media_stream_audio_processor.cc
@@ -247,6 +247,14 @@ void MediaStreamAudioProcessor::OnPlayoutData(media::AudioBus* audio_bus,
     audio_processing_->AnalyzeReverseStream(&render_frame_);
 }
 
+void MediaStreamAudioProcessor::OnPlayoutDataSourceChanged() {
+  DCHECK(main_thread_checker_.CalledOnValidThread());
+  // There is no need to hold a lock here since the caller guarantees that
+  // there is no more OnPlayoutData() callback on the render thread.
+  render_thread_checker_.DetachFromThread();
+  render_converter_.reset();
+}
+
 void MediaStreamAudioProcessor::GetStats(AudioProcessorStats* stats) {
   stats->typing_noise_detected =
       (base::subtle::Acquire_Load(&typing_detected_) != false);