Combining SetVideoSend and SetSource into one method.

webrtc/api/rtpsender.cc

Index: webrtc/api/rtpsender.cc
diff --git a/webrtc/api/rtpsender.cc b/webrtc/api/rtpsender.cc
index 5577b9c7500457714491f75950bafad839751354..33d7ee37a9f3c92ad4e3e1c6af55583603e10762 100644
--- a/webrtc/api/rtpsender.cc
+++ b/webrtc/api/rtpsender.cc
@@ -280,7 +280,7 @@ bool VideoRtpSender::SetTrack(MediaStreamTrackInterface* track) {
   // Attach to new track.
   bool prev_can_send_track = can_send_track();
   // Keep a reference to the old track to keep it alive until we call
-  // SetSource.
+  // SetVideoSend.
   rtc::scoped_refptr<VideoTrackInterface> old_track = track_;
   track_ = video_track;
   if (track_) {
@@ -290,17 +290,9 @@ bool VideoRtpSender::SetTrack(MediaStreamTrackInterface* track) {
 
   // Update video provider.
   if (can_send_track()) {
-    // TODO(deadbeef): If SetTrack is called with a disabled track, and the
-    // previous track was enabled, this could cause a frame from the new track
-    // to slip out. Really, what we need is for SetSource and SetVideoSend
-    // to be combined into one atomic operation, all the way down to
-    // WebRtcVideoSendStream.
-
-    provider_->SetSource(ssrc_, track_);
     SetVideoSend();
   } else if (prev_can_send_track) {
-    provider_->SetSource(ssrc_, nullptr);
-    provider_->SetVideoSend(ssrc_, false, nullptr);
+    ClearVideoSend();
   }
   return true;
 }
@@ -312,12 +304,10 @@ void VideoRtpSender::SetSsrc(uint32_t ssrc) {
   }
   // If we are already sending with a particular SSRC, stop sending.
   if (can_send_track()) {
-    provider_->SetSource(ssrc_, nullptr);
-    provider_->SetVideoSend(ssrc_, false, nullptr);
+    ClearVideoSend();
   }
   ssrc_ = ssrc;
   if (can_send_track()) {
-    provider_->SetSource(ssrc_, track_);
     SetVideoSend();
   }
 }
@@ -332,8 +322,7 @@ void VideoRtpSender::Stop() {
     track_->UnregisterObserver(this);
   }
   if (can_send_track()) {
-    provider_->SetSource(ssrc_, nullptr);
-    provider_->SetVideoSend(ssrc_, false, nullptr);
+    ClearVideoSend();
   }
   stopped_ = true;
 }
@@ -346,7 +335,13 @@ void VideoRtpSender::SetVideoSend() {
     options.is_screencast = rtc::Optional<bool>(source->is_screencast());
     options.video_noise_reduction = source->needs_denoising();
   }
-  provider_->SetVideoSend(ssrc_, track_->enabled(), &options);
+  provider_->SetVideoSend(ssrc_, track_->enabled(), &options, track_);
+}
+
+void VideoRtpSender::ClearVideoSend() {
+  RTC_DCHECK(ssrc_ != 0);
+  RTC_DCHECK(provider_ != nullptr);
+  provider_->SetVideoSend(ssrc_, false, nullptr, nullptr);
 }
 
 RtpParameters VideoRtpSender::GetParameters() const {