Wire up FlexfecSender in RTP module and VideoSendStream.

webrtc/modules/rtp_rtcp/include/rtp_rtcp.h

Index: webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
diff --git a/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h b/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
index a2c7098722baa52776be24eefecdd3ce7f828e73..830d895774d2559ece632a707c7b73ee91949b4f 100644
--- a/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
+++ b/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
@@ -20,6 +20,7 @@
 #include "webrtc/base/deprecation.h"
 #include "webrtc/base/optional.h"
 #include "webrtc/modules/include/module.h"
+#include "webrtc/modules/rtp_rtcp/include/flexfec_sender.h"
 #include "webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h"
 #include "webrtc/modules/video_coding/include/video_coding_defines.h"
 
@@ -76,6 +77,10 @@ class RtpRtcp : public Module {
     // Spread any bursts of packets into smaller bursts to minimize packet loss.
     RtpPacketSender* paced_sender = nullptr;
 
+    // Generate FlexFEC packets.
+    // TODO(brandtr): Remove when FlexfecSender is wired up to PacedSender.
+    FlexfecSender* flexfec_sender = nullptr;
+
     TransportSequenceNumberAllocator* transport_sequence_number_allocator =
         nullptr;
     BitrateStatisticsObserver* send_bitrate_observer = nullptr;