Set up receiver RTX config using a std::map.

This change removes video_payload_type from RtxConfig as it can be
inferred from the map key or config otherwise. Wiring up this config is
part of issue 2399.

BUG=
R=mflodman@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/7349004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@5402 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/video_receive_stream.h b/video_receive_stream.h
index 55e5a62..ac1afc6 100644
--- a/video_receive_stream.h
+++ b/video_receive_stream.h
@@ -11,6 +11,7 @@
 #ifndef WEBRTC_VIDEO_RECEIVE_STREAM_H_
 #define WEBRTC_VIDEO_RECEIVE_STREAM_H_
 
+#include <map>
 #include <string>
 #include <vector>
 
@@ -137,9 +138,9 @@
       // See FecConfig for description.
       FecConfig fec;
 
-      // RTX settings for possible payloads. RTX is disabled if the vector is
-      // empty.
-      std::vector<RtxConfig> rtx;
+      // RTX settings for video payloads that may be received. RTX is disabled
+      // if there's no config present.
+      std::map<int, RtxConfig> rtx;
 
       // RTP header extensions used for the received stream.
       std::vector<RtpExtension> extensions;