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

webrtc/video/rtp_stream_receiver.cc

Index: webrtc/video/rtp_stream_receiver.cc
diff --git a/webrtc/video/rtp_stream_receiver.cc b/webrtc/video/rtp_stream_receiver.cc
index 8777535a25abb3f98e0b6d80e0a509383666f3d8..a63ae280f23489803f491bfbd4ca538cd61585d8 100644
--- a/webrtc/video/rtp_stream_receiver.cc
+++ b/webrtc/video/rtp_stream_receiver.cc
@@ -152,14 +152,13 @@ RtpStreamReceiver::RtpStreamReceiver(
                                            : kDefaultMaxReorderingThreshold;
   rtp_receive_statistics_->SetMaxReorderingThreshold(max_reordering_threshold);
 
-  // TODO(pbos): Support multiple RTX, per video payload.
-  for (const auto& kv : config_.rtp.rtx) {
-    RTC_DCHECK(kv.second.ssrc != 0);
-    RTC_DCHECK(kv.second.payload_type != 0);
-
-    rtp_payload_registry_.SetRtxSsrc(kv.second.ssrc);
-    rtp_payload_registry_.SetRtxPayloadType(kv.second.payload_type,
-                                            kv.first);
+  if (config_.rtp.rtx_ssrc) {
+    rtp_payload_registry_.SetRtxSsrc(config_.rtp.rtx_ssrc);
+
+    for (const auto& kv : config_.rtp.rtx_payload_types) {
+      RTC_DCHECK(kv.second != 0);
+      rtp_payload_registry_.SetRtxPayloadType(kv.second, kv.first);
+    }
   }
 
   if (IsUlpfecEnabled()) {