Reverse |rtx_payload_types| map, and rename.

webrtc/video/rtp_video_stream_receiver.cc

Index: webrtc/video/rtp_video_stream_receiver.cc
diff --git a/webrtc/video/rtp_video_stream_receiver.cc b/webrtc/video/rtp_video_stream_receiver.cc
index 01cb4dcc2fb43e8a519c7fbee03e9c228ec5c9f8..4678b8f0afff36cea95279d27b21812cb3f8a5eb 100644
--- a/webrtc/video/rtp_video_stream_receiver.cc
+++ b/webrtc/video/rtp_video_stream_receiver.cc
@@ -148,9 +148,9 @@ RtpVideoStreamReceiver::RtpVideoStreamReceiver(
   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);
+    for (const auto& kv : config_.rtp.rtx_associated_payload_types) {
+      RTC_DCHECK_NE(kv.first, 0);
+      rtp_payload_registry_.SetRtxPayloadType(kv.first, kv.second);
     }
   }