Refactor: simplify interface of SenderRtcpSession and CastTransport.

media/cast/net/rtcp/rtcp_defines.h

Index: media/cast/net/rtcp/rtcp_defines.h
diff --git a/media/cast/net/rtcp/rtcp_defines.h b/media/cast/net/rtcp/rtcp_defines.h
index a78a1d7d504106f34137d534e5ae72e095772806..51f39259aae4396dd173a2a53c6e4cf1f21d6a75 100644
--- a/media/cast/net/rtcp/rtcp_defines.h
+++ b/media/cast/net/rtcp/rtcp_defines.h
@@ -126,12 +126,6 @@ struct RtcpEvent {
   uint16_t packet_id;
 };
 
-typedef base::Callback<void(const RtcpCastMessage&)> RtcpCastMessageCallback;
-typedef base::Callback<void(base::TimeDelta)> RtcpRttCallback;
-typedef
-base::Callback<void(const RtcpReceiverLogMessage&)> RtcpLogMessageCallback;
-typedef base::Callback<void()> RtcpPliCallback;
-
 // TODO(hubbe): Document members of this struct.
 struct RtpReceiverStatistics {
   RtpReceiverStatistics();