Add Cast PLI support on sender side.

media/cast/net/rtcp/receiver_rtcp_session.cc

Index: media/cast/net/rtcp/receiver_rtcp_session.cc
diff --git a/media/cast/net/rtcp/receiver_rtcp_session.cc b/media/cast/net/rtcp/receiver_rtcp_session.cc
index ba917da6155be5ef2728e7f403a4dad78aba6759..51e77ad451f1d3b23af4c0c9c58811511eff749f 100644
--- a/media/cast/net/rtcp/receiver_rtcp_session.cc
+++ b/media/cast/net/rtcp/receiver_rtcp_session.cc
@@ -99,6 +99,7 @@ void ReceiverRtcpSession::OnReceivedNtp(uint32_t ntp_seconds,
 void ReceiverRtcpSession::SendRtcpReport(
     RtcpTimeData time_data,
     const RtcpCastMessage* cast_message,
+    const RtcpPliMessage* pli_message,
     base::TimeDelta target_delay,
     const ReceiverRtcpEventSubscriber::RtcpEvents* rtcp_events,
     const RtpReceiverStatistics* rtp_receiver_statistics) const {
@@ -128,11 +129,12 @@ void ReceiverRtcpSession::SendRtcpReport(
       report_block.delay_since_last_sr = 0;
     }
   }
+
   RtcpBuilder rtcp_builder(local_ssrc_);
   packet_sender_->SendRtcpPacket(
       local_ssrc_, rtcp_builder.BuildRtcpFromReceiver(
-                       rtp_receiver_statistics ? &report_block : NULL, &rrtr,
-                       cast_message, rtcp_events, target_delay));
+                       rtp_receiver_statistics ? &report_block : nullptr, &rrtr,
+                       cast_message, pli_message, rtcp_events, target_delay));
 }
 
 void ReceiverRtcpSession::OnReceivedLipSyncInfo(RtpTimeTicks rtp_timestamp,