Add Cast PLI support on sender side.

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 71f2291c6dc7130db0e45d5a71ccb43294140e14..3455d4f5360491e6c687e0f91d9f5a85d0c20b98 100644
--- a/media/cast/net/rtcp/rtcp_defines.h
+++ b/media/cast/net/rtcp/rtcp_defines.h
@@ -48,7 +48,7 @@ struct RtcpCastMessage {
   RtcpCastMessage();
   ~RtcpCastMessage();
 
-  uint32_t media_ssrc;
+  uint32_t remote_ssrc;
   uint32_t ack_frame_id;
   uint16_t target_delay_ms;
   MissingFramesAndPacketsMap missing_frames_and_packets;
@@ -60,6 +60,13 @@ struct RtcpCastMessage {
   std::vector<uint32_t> received_later_frames;
 };
 
+struct RtcpPliMessage {
+  explicit RtcpPliMessage(uint32_t ssrc);
+  RtcpPliMessage();
+
+  uint32_t remote_ssrc;
+};
+
 // Log messages from receiver to sender.
 struct RtcpReceiverEventLogMessage {
   RtcpReceiverEventLogMessage();
@@ -123,6 +130,7 @@ 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 {
@@ -149,6 +157,7 @@ struct SendRtcpFromRtpReceiver_Params {
   uint32_t sender_ssrc;
   RtcpTimeData time_data;
   scoped_ptr<RtcpCastMessage> cast_message;
+  scoped_ptr<RtcpPliMessage> pli_message;
   base::TimeDelta target_delay;
   scoped_ptr<std::vector<std::pair<RtpTimeTicks, RtcpEvent>>> rtcp_events;
   scoped_ptr<RtpReceiverStatistics> rtp_receiver_statistics;