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

webrtc/api/videocapturertracksource.cc

Index: webrtc/api/videocapturertracksource.cc
diff --git a/webrtc/api/videocapturertracksource.cc b/webrtc/api/videocapturertracksource.cc
index 1bf4bea1d0d779ec93eff06e55b73f1ebd998572..f8897a28461cdc4337b2fca2c5ccbbb47d3810a3 100644
--- a/webrtc/api/videocapturertracksource.cc
+++ b/webrtc/api/videocapturertracksource.cc
@@ -320,6 +320,9 @@ void VideoCapturerTrackSource::Initialize(
     }
   }
 
+  // Get default from the capturer, overridden by constraints, if any.
+  needs_denoising_ = video_capturer_->NeedsDenoising();
+
   if (constraints) {
     MediaConstraintsInterface::Constraints mandatory_constraints =
         constraints->GetMandatory();