Add method cricket::VideoCapturer::NeedsDenoising, use in VideoCapturerTrackSource.

webrtc/media/base/videocapturer.h

Index: webrtc/media/base/videocapturer.h
diff --git a/webrtc/media/base/videocapturer.h b/webrtc/media/base/videocapturer.h
index c9c96eeb1d299cb06eaad73c8d4734cfdc357eac..af982a97115e30562597cc3cc94a512e9aa02fce 100644
--- a/webrtc/media/base/videocapturer.h
+++ b/webrtc/media/base/videocapturer.h
@@ -175,6 +175,11 @@ class VideoCapturer : public sigslot::has_slots<>,
   // implement screencast specific behavior.
   virtual bool IsScreencast() const = 0;
 
+  // Returns denoising preference. Unset means use encoder-specific default.
+  virtual rtc::Optional<bool> NeedsDenoising() const {
+    return rtc::Optional<bool>();
+  }
+
   // Caps the VideoCapturer's format according to max_format. It can e.g. be
   // used to prevent cameras from capturing at a resolution or framerate that
   // the capturer is capable of but not performing satisfactorily at.