cast: Split Rtcp into two for sender and receiver

media/cast/net/cast_transport_config.h

Index: media/cast/net/cast_transport_config.h
diff --git a/media/cast/net/cast_transport_config.h b/media/cast/net/cast_transport_config.h
index b4427dfb87d2ebb0283a2f8bc571b6a96f9b3142..80a6738f9b3efef580fb91fcbd8597727f3a05fd 100644
--- a/media/cast/net/cast_transport_config.h
+++ b/media/cast/net/cast_transport_config.h
@@ -143,7 +143,7 @@ struct RtcpSenderInfo {
   RtcpSenderInfo();
   ~RtcpSenderInfo();
   // First three members are used for lipsync.
-  // First two members are used for rtt.
+  // Last two members are used for rtt.
   uint32 ntp_seconds;
   uint32 ntp_fraction;
   RtpTimeTicks rtp_timestamp;