Reverse |rtx_payload_types| map, and rename.

webrtc/media/engine/webrtcvideoengine.cc

Index: webrtc/media/engine/webrtcvideoengine.cc
diff --git a/webrtc/media/engine/webrtcvideoengine.cc b/webrtc/media/engine/webrtcvideoengine.cc
index 8a23ae8b441a139b947461bb53d2535077fad17c..6808f2c59afedc7d468b9326cc3350510244206a 100644
--- a/webrtc/media/engine/webrtcvideoengine.cc
+++ b/webrtc/media/engine/webrtcvideoengine.cc
@@ -2219,10 +2219,10 @@ void WebRtcVideoChannel::WebRtcVideoReceiveStream::ConfigureCodecs(
     config_.decoders.push_back(decoder);
   }
 
-  config_.rtp.rtx_payload_types.clear();
+  config_.rtp.rtx_associated_payload_types.clear();
   for (const VideoCodecSettings& recv_codec : recv_codecs) {
-    config_.rtp.rtx_payload_types[recv_codec.codec.id] =
-        recv_codec.rtx_payload_type;
+    config_.rtp.rtx_associated_payload_types[recv_codec.rtx_payload_type] =
+        recv_codec.codec.id;
   }
 
   config_.rtp.ulpfec = recv_codecs.front().ulpfec;