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 e8acf48b00f4ee376bed8ad338f8428d7a438611..c4081f3a7616f0204bb76f3d1d31b738d34673dd 100644
--- a/webrtc/video/rtp_stream_receiver.cc
+++ b/webrtc/video/rtp_stream_receiver.cc
@@ -150,14 +150,13 @@ 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()) {