Add |protected_by_flexfec| flag to VideoReceiveStream::Config.

webrtc/media/engine/webrtcvideoengine2.cc

Index: webrtc/media/engine/webrtcvideoengine2.cc
diff --git a/webrtc/media/engine/webrtcvideoengine2.cc b/webrtc/media/engine/webrtcvideoengine2.cc
index c192b52402ee95ef3f2ffd9dbe25f65ded5ecf6d..f3d16ff2730454cd00e6540f6107a7ae26587a32 100644
--- a/webrtc/media/engine/webrtcvideoengine2.cc
+++ b/webrtc/media/engine/webrtcvideoengine2.cc
@@ -2295,12 +2295,20 @@ void WebRtcVideoChannel2::WebRtcVideoReceiveStream::RecreateWebRtcStream() {
     call_->DestroyFlexfecReceiveStream(flexfec_stream_);
     flexfec_stream_ = nullptr;
   }
-  if (IsFlexfecFieldTrialEnabled() && flexfec_config_.IsCompleteAndEnabled()) {
+
+  const bool use_flexfec =
+      IsFlexfecFieldTrialEnabled() && flexfec_config_.IsCompleteAndEnabled();
+  // TODO(nisse): There are way too many copies here. And why isn't
+  // the argument to CreateVideoReceiveStream a const ref?

[brandtr, 2017/02/23 11:58:32]

Agree that this should be cleaned up at some point. Right now, its a mixture of
copies and moves in the code that has to do with the VideoReceiveStream::Config.

[nisse-webrtc, 2017/02/23 13:01:22]

I noticed a std::move(configuration) in Call::CreateVideoReceiveStream, 
but it's not clear to me if it makes any difference.

Is there any easy way to eliminate at least the second Copy call here?

[brandtr, 2017/02/23 15:28:35]

I guess that std::move saves a copy at that call site.

I'm not sure if removing the copy here would change the logic overall in any
way. It might be good to be careful, it's my experience that it is fairly easy
to introduce bugs -- that are not found by tests -- in the configuration at this
layer.

+  webrtc::VideoReceiveStream::Config config = config_.Copy();
+  config.rtp.protected_by_flexfec = use_flexfec;
+  stream_ = call_->CreateVideoReceiveStream(config.Copy());
+  stream_->Start();
+
+  if (use_flexfec) {
     flexfec_stream_ = call_->CreateFlexfecReceiveStream(flexfec_config_);
     flexfec_stream_->Start();
   }
-  stream_ = call_->CreateVideoReceiveStream(config_.Copy());
-  stream_->Start();
 }
 
 void WebRtcVideoChannel2::WebRtcVideoReceiveStream::ClearDecoders(