Get VideoCapturer stats via VideoTrackSourceInterface in StatsCollector,

webrtc/api/videocapturertracksource.cc

Index: webrtc/api/videocapturertracksource.cc
diff --git a/webrtc/api/videocapturertracksource.cc b/webrtc/api/videocapturertracksource.cc
index e292c7a065ce2dcb828d101df67a0188be5e7f3e..16e89c853dd8a6f54bfbc2cd43750a8ea3120f17 100644
--- a/webrtc/api/videocapturertracksource.cc
+++ b/webrtc/api/videocapturertracksource.cc
@@ -362,6 +362,15 @@ void VideoCapturerTrackSource::Initialize(
   // Initialize hasn't succeeded until a successful state change has occurred.
 }
 
+bool VideoCapturerTrackSource::GetStats(Stats* stats) {
+  cricket::VideoFormat last_captured_frame_format;
+  video_capturer_->GetStats(&last_captured_frame_format);
+  stats->input_width = last_captured_frame_format.width;
+  stats->input_height = last_captured_frame_format.height;
+
+  return true;
+}
+
 void VideoCapturerTrackSource::Stop() {
   if (!started_) {
     return;