Remove RED/RTX workaround from sender/receiver and VideoEngine2.

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 576543bef682d05aa6cabef4790da3bb44fb76b7..9b0d08bacfc6855f54fb262457c2e17ce89be346 100644
--- a/webrtc/video/rtp_stream_receiver.cc
+++ b/webrtc/video/rtp_stream_receiver.cc
@@ -152,15 +152,6 @@ RtpStreamReceiver::RtpStreamReceiver(
                                             kv.first);
   }
 
-  // If set to true, the RTX payload type mapping supplied in
-  // |SetRtxPayloadType| will be used when restoring RTX packets. Without it,
-  // RTX packets will always be restored to the last non-RTX packet payload type
-  // received.
-  // TODO(holmer): When Chrome no longer depends on this being false by default,
-  // always use the mapping and remove this whole codepath.
-  rtp_payload_registry_.set_use_rtx_payload_mapping_on_restore(
-      config_.rtp.use_rtx_payload_mapping_on_restore);
-
   if (IsFecEnabled()) {
     VideoCodec ulpfec_codec = {};
     ulpfec_codec.codecType = kVideoCodecULPFEC;