Add Cast PLI support on sender side.

media/cast/net/rtcp/rtcp_defines.cc

Index: media/cast/net/rtcp/rtcp_defines.cc
diff --git a/media/cast/net/rtcp/rtcp_defines.cc b/media/cast/net/rtcp/rtcp_defines.cc
index b4f363e30a14625b286a94eb5936f840244b57ad..c493b6cc7d2cf65af513888a71e762f2b0b7e0cc 100644
--- a/media/cast/net/rtcp/rtcp_defines.cc
+++ b/media/cast/net/rtcp/rtcp_defines.cc
@@ -10,11 +10,15 @@ namespace media {
 namespace cast {
 
 RtcpCastMessage::RtcpCastMessage(uint32_t ssrc)
-    : media_ssrc(ssrc), ack_frame_id(0u), target_delay_ms(0) {}
+    : remote_ssrc(ssrc), ack_frame_id(0u), target_delay_ms(0) {}
 RtcpCastMessage::RtcpCastMessage()
-    : media_ssrc(0), ack_frame_id(0u), target_delay_ms(0) {}
+    : remote_ssrc(0), ack_frame_id(0u), target_delay_ms(0) {}
 RtcpCastMessage::~RtcpCastMessage() {}
 
+RtcpPliMessage::RtcpPliMessage(uint32_t ssrc) : remote_ssrc(ssrc) {}
+RtcpPliMessage::RtcpPliMessage() : remote_ssrc(0) {}
+RtcpPliMessage::~RtcpPliMessage() {}
+
 RtcpReceiverEventLogMessage::RtcpReceiverEventLogMessage()
     : type(UNKNOWN), packet_id(0u) {}
 RtcpReceiverEventLogMessage::~RtcpReceiverEventLogMessage() {}