Inform jitter buffer about FlexFEC protection.

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 9e7f5c4bd45fdb49a2493d94a6a83600073d88b2..d97541a3731a73227eb5be321970d8b6400eb9ef 100644
--- a/webrtc/media/engine/webrtcvideoengine2.cc
+++ b/webrtc/media/engine/webrtcvideoengine2.cc
@@ -2286,11 +2286,13 @@ void WebRtcVideoChannel2::WebRtcVideoReceiveStream::RecreateWebRtcStream() {
     call_->DestroyVideoReceiveStream(stream_);
   }
   stream_ = call_->CreateVideoReceiveStream(config_.Copy());
-  stream_->Start();
   if (IsFlexfecFieldTrialEnabled() && flexfec_config_.IsCompleteAndEnabled()) {
     flexfec_stream_ = call_->CreateFlexfecReceiveStream(flexfec_config_);
     flexfec_stream_->Start();
   }
+  // Start VideoReceiveStream after FlexfecReceiveStream has been created,
+  // so that the former is aware of the existence of the latter.
+  stream_->Start();
 }
 
 void WebRtcVideoChannel2::WebRtcVideoReceiveStream::ClearDecoders(