Cast: Re-factor rtcp_sender.cc into rtcp_builder.cc and do some cleanup

media/cast/net/rtcp/rtcp.cc

Index: media/cast/net/rtcp/rtcp.cc
diff --git a/media/cast/net/rtcp/rtcp.cc b/media/cast/net/rtcp/rtcp.cc
index 6b7718dde90347de921c3385c4a97ce498ee0295..317c8d8194a2e3cb209484e514922e5d755de658 100644
--- a/media/cast/net/rtcp/rtcp.cc
+++ b/media/cast/net/rtcp/rtcp.cc
@@ -8,8 +8,9 @@
 #include "media/cast/cast_defines.h"
 #include "media/cast/cast_environment.h"
 #include "media/cast/net/cast_transport_defines.h"
+#include "media/cast/net/pacing/paced_sender.h"
+#include "media/cast/net/rtcp/rtcp_builder.h"
 #include "media/cast/net/rtcp/rtcp_defines.h"
-#include "media/cast/net/rtcp/rtcp_sender.h"
 #include "media/cast/net/rtcp/rtcp_utility.h"
 
 using base::TimeDelta;
@@ -64,7 +65,8 @@ Rtcp::Rtcp(const RtcpCastMessageCallback& cast_callback,
       rtt_callback_(rtt_callback),
       log_callback_(log_callback),
       clock_(clock),
-      rtcp_sender_(new RtcpSender(packet_sender, local_ssrc)),
+      rtcp_builder_(new RtcpBuilder(local_ssrc)),
+      packet_sender_(packet_sender),
       local_ssrc_(local_ssrc),
       remote_ssrc_(remote_ssrc),
       last_report_truncated_ntp_(0),
@@ -228,12 +230,14 @@ void Rtcp::SendRtcpFromRtpReceiver(
       report_block.delay_since_last_sr = 0;
     }
   }
-  rtcp_sender_->SendRtcpFromRtpReceiver(
-      rtp_receiver_statistics ? &report_block : NULL,
-      &rrtr,
-      cast_message,
-      rtcp_events,
-      target_delay);
+  packet_sender_->SendRtcpPacket(
+      local_ssrc_,
+      rtcp_builder_->BuildRtcpFromReceiver(
+          rtp_receiver_statistics ? &report_block : NULL,
+          &rrtr,
+          cast_message,
+          rtcp_events,
+          target_delay));
 }
 
 void Rtcp::SendRtcpFromRtpSender(base::TimeTicks current_time,
@@ -254,7 +258,9 @@ void Rtcp::SendRtcpFromRtpSender(base::TimeTicks current_time,
   sender_info.send_packet_count = send_packet_count;
   sender_info.send_octet_count = send_octet_count;
 
-  rtcp_sender_->SendRtcpFromRtpSender(sender_info);
+  packet_sender_->SendRtcpPacket(
+      local_ssrc_,
+      rtcp_builder_->BuildRtcpFromSender(sender_info));
 }
 
 void Rtcp::OnReceivedNtp(uint32 ntp_seconds, uint32 ntp_fraction) {