Wire up FlexfecSender in RTPSenderVideo.

webrtc/modules/rtp_rtcp/source/flexfec_sender.cc

Index: webrtc/modules/rtp_rtcp/source/flexfec_sender.cc
diff --git a/webrtc/modules/rtp_rtcp/source/flexfec_sender.cc b/webrtc/modules/rtp_rtcp/source/flexfec_sender.cc
index 55e8e5266919bbb978b44e8d5fcd1fff356549c1..4b0df09c4226bfc0f1dcea1a0cae150e0d347393 100644
--- a/webrtc/modules/rtp_rtcp/source/flexfec_sender.cc
+++ b/webrtc/modules/rtp_rtcp/source/flexfec_sender.cc
@@ -83,6 +83,13 @@ FlexfecSender::FlexfecSender(
                       << ", is unsupported by FlexfecSender.";
     }
   }
+
+  // Calculate RTP header length.
+  RtpPacketToSend rtp_header(&rtp_header_extension_map_);
+  rtp_header.ReserveExtension<AbsoluteSendTime>();
+  rtp_header.ReserveExtension<TransmissionOffset>();
+  rtp_header.ReserveExtension<TransportSequenceNumber>();
+  rtp_header_length_ = rtp_header.headers_size();

[danilchap, 2016/11/09 15:58:46]

that should be simpler:
rtp_extra_header_length_ = rtp_header_extension_map_.GetTotalLengthInBytes();
(since you do not use csrcs in the flexfec, the only header size over base 12
bytes are extensions)

[brandtr, 2016/11/10 09:32:01]

Nice, done.

 }
 
 FlexfecSender::~FlexfecSender() = default;