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.

[perkj_webrtc, 2016/09/14 13:08:27]

This should not have anything todo with an encoder. So I think this comment
should not mention an encoder.
 

[nisse-webrtc, 2016/09/14 13:20:23]

Behavior if unset depends on the encoder. I think that's relevant.   

[perkj_webrtc, 2016/09/14 13:28:22]

Can you elaborate on this. To me- the whole thing is very weird and hacky. Is
there a better comment in VideoTrackSource? 
Maybe also add a todo and a comment why this is added at all here.

+  virtual rtc::Optional<bool> NeedsDenoising() const {

[perkj_webrtc, 2016/09/14 13:08:27]

Also - I think this api should be identical to IsScreenCast. 
Its the same hack. 
virtual bool NeedsDenoising() { return false; }

[nisse-webrtc, 2016/09/14 13:20:23]

I'm afraid it has to be three-state, it's passed on to be returned by
VideoCapturerTrackSource::needs_denoising, then copied into VideoOptions for
SetVideoSend by VideoRtpSender.

For consistency, we could change IsScreencast to the three-state too, but I
don't think that is a real improvement.

[perkj_webrtc, 2016/09/14 13:28:22]

Acknowledged.

+    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.