Add sending Nack to RtcpTransceiver

Bug: webrtc:8239
Change-Id: Idf27bb05958d9eceaf601078019f05444232581f
Reviewed-on: https://webrtc-review.googlesource.com/26260
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20907}
diff --git a/modules/rtp_rtcp/source/rtcp_transceiver_impl.h b/modules/rtp_rtcp/source/rtcp_transceiver_impl.h
index a89f3e1..8cde921 100644
--- a/modules/rtp_rtcp/source/rtcp_transceiver_impl.h
+++ b/modules/rtp_rtcp/source/rtcp_transceiver_impl.h
@@ -44,6 +44,8 @@
   void SetRemb(int bitrate_bps, std::vector<uint32_t> ssrcs);
   void UnsetRemb();
 
+  void SendNack(uint32_t ssrc, std::vector<uint16_t> sequence_numbers);
+
   void SendPictureLossIndication(rtc::ArrayView<const uint32_t> ssrcs);
   void SendFullIntraRequest(rtc::ArrayView<const uint32_t> ssrcs);