Reland of Make RTX pt/apt reconfigurable by calling WebRtcVideoChannel2::SetRecvParameters.

webrtc/call/call.cc

Index: webrtc/call/call.cc
diff --git a/webrtc/call/call.cc b/webrtc/call/call.cc
index d37d08ef8e7ac824669c787f6672ac633d1648d3..ac9866b314714cd8e45167872b8f8f47219fa4f0 100644
--- a/webrtc/call/call.cc
+++ b/webrtc/call/call.cc
@@ -649,11 +649,8 @@ webrtc::VideoReceiveStream* Call::CreateVideoReceiveStream(
     RTC_DCHECK(video_receive_ssrcs_.find(config.rtp.remote_ssrc) ==
                video_receive_ssrcs_.end());
     video_receive_ssrcs_[config.rtp.remote_ssrc] = receive_stream;
-    // TODO(pbos): Configure different RTX payloads per receive payload.
-    VideoReceiveStream::Config::Rtp::RtxMap::const_iterator it =
-        config.rtp.rtx.begin();
-    if (it != config.rtp.rtx.end())
-      video_receive_ssrcs_[it->second.ssrc] = receive_stream;
+    if (config.rtp.rtx_ssrc)
+      video_receive_ssrcs_[config.rtp.rtx_ssrc] = receive_stream;
     video_receive_streams_.insert(receive_stream);
     ConfigureSync(config.sync_group);
   }