Change VideoSourceInterface::needs_denoising() to return rtc::Optional<bool>

webrtc/api/videotracksource.h

Index: webrtc/api/videotracksource.h
diff --git a/webrtc/api/videotracksource.h b/webrtc/api/videotracksource.h
index 78577aaba23b1f4e4efe345a3cf5fd4e875c8b28..6d23d2e8cace164a949e923482f148e6c6bc3293 100644
--- a/webrtc/api/videotracksource.h
+++ b/webrtc/api/videotracksource.h
@@ -37,7 +37,8 @@ class VideoTrackSource : public Notifier<VideoTrackSourceInterface> {
   void Restart() override{};
 
   virtual bool is_screencast() const { return false; }
-  virtual bool needs_denoising() const { return false; }
+  virtual rtc::Optional<bool> needs_denoising() const {
+    return rtc::Optional<bool>(); }
 
   void AddOrUpdateSink(rtc::VideoSinkInterface<cricket::VideoFrame>* sink,
                        const rtc::VideoSinkWants& wants) override;