Fix for scenario where m-line is revived after being set to port 0.

talk/app/webrtc/rtpsender.cc

Index: talk/app/webrtc/rtpsender.cc
diff --git a/talk/app/webrtc/rtpsender.cc b/talk/app/webrtc/rtpsender.cc
index 3a78f4598a8d359a6c34b1a93071250a4a1a8114..425d159d5f8904e9d125a7fd595cd9391ae7476c 100644
--- a/talk/app/webrtc/rtpsender.cc
+++ b/talk/app/webrtc/rtpsender.cc
@@ -144,10 +144,6 @@ VideoRtpSender::VideoRtpSender(VideoTrackInterface* track,
       provider_(provider),
       cached_track_enabled_(track->enabled()) {
   track_->RegisterObserver(this);
-  VideoSourceInterface* source = track_->GetSource();
-  if (source) {
-    provider_->SetCaptureDevice(ssrc_, source->GetVideoCapturer());
-  }
   Reconfigure();
 }
 
@@ -159,7 +155,7 @@ VideoRtpSender::~VideoRtpSender() {
 void VideoRtpSender::OnChanged() {
   if (cached_track_enabled_ != track_->enabled()) {
     cached_track_enabled_ = track_->enabled();
-    Reconfigure();
+    SetVideoSend();
   }
 }
 
@@ -196,8 +192,19 @@ void VideoRtpSender::Reconfigure() {
   if (!provider_) {
     return;
   }
-  const cricket::VideoOptions* options = nullptr;
   VideoSourceInterface* source = track_->GetSource();
+  if (source) {
+    provider_->SetCaptureDevice(ssrc_, source->GetVideoCapturer());

[pthatcher1, 2015/11/11 00:45:02]

Is there any downside to calling this all the time?  In other words, to just
call Reconfigure() all the time and not have a separate SetVideoSend?

[Taylor Brandstetter, 2015/11/11 01:33:30]

If you trace your way down to
WebRtcVideoChannel2::WebRtcVideoSendStream::SetCapturer, it definitely seems to
have some undesired effects. I plan to merge SetVideoSend and SetCapturer in a
later CL though, and then we can get rid of "ReconfigureEverythingButCapturer"

+  }
+  SetVideoSend();
+}
+
+void VideoRtpSender::SetVideoSend() {

[pthatcher1, 2015/11/11 00:45:02]

Actually, if this is separate, calling something like "ReconfigureJustX" or
"ReconfigureEverythingExceptX" might make sense.  Perhaps
"ReconfigureEverythingExceptCaptureDevice".  It's verbose, but it's at least
clear what the intention is.

[Taylor Brandstetter, 2015/11/11 01:33:30]

Done.

+  if (!provider_) {
+    return;
+  }
+  VideoSourceInterface* source = track_->GetSource();
+  const cricket::VideoOptions* options = nullptr;
   if (track_->enabled() && source) {
     options = source->options();
   }