Add Cast PLI support on sender side.

media/cast/net/rtcp/rtcp_builder.cc

Index: media/cast/net/rtcp/rtcp_builder.cc
diff --git a/media/cast/net/rtcp/rtcp_builder.cc b/media/cast/net/rtcp/rtcp_builder.cc
index cd7652307837fa64314ba4607b7c62d34c0954e6..bcedc7d2f3974771a7adc72d0eda040a086aad9f 100644
--- a/media/cast/net/rtcp/rtcp_builder.cc
+++ b/media/cast/net/rtcp/rtcp_builder.cc
@@ -165,6 +165,7 @@ PacketRef RtcpBuilder::BuildRtcpFromReceiver(
     const RtcpReportBlock* report_block,
     const RtcpReceiverReferenceTimeReport* rrtr,
     const RtcpCastMessage* cast_message,
+    const RtcpPliMessage* pli_message,
     const ReceiverRtcpEventSubscriber::RtcpEvents* rtcp_events,
     base::TimeDelta target_delay) {
   Start();
@@ -175,6 +176,8 @@ PacketRef RtcpBuilder::BuildRtcpFromReceiver(
     AddRrtr(rrtr);
   if (cast_message)
     AddCast(cast_message, target_delay);
+  if (pli_message)
+    AddPli(pli_message);
   if (rtcp_events)
     AddReceiverLog(*rtcp_events);
 
@@ -227,12 +230,18 @@ void RtcpBuilder::AddRrtr(const RtcpReceiverReferenceTimeReport* rrtr) {
   writer_.WriteU32(rrtr->ntp_fraction);
 }
 
+void RtcpBuilder::AddPli(const RtcpPliMessage* pli_message) {
+  AddRtcpHeader(kPacketTypePayloadSpecific, 1);
+  writer_.WriteU32(ssrc_);
+  writer_.WriteU32(pli_message->remote_ssrc);
+}
+
 void RtcpBuilder::AddCast(const RtcpCastMessage* cast,
                           base::TimeDelta target_delay) {
   // See RTC 4585 Section 6.4 for application specific feedback messages.
   AddRtcpHeader(kPacketTypePayloadSpecific, 15);
   writer_.WriteU32(ssrc_);              // Add our own SSRC.
-  writer_.WriteU32(cast->media_ssrc);  // Remote SSRC.
+  writer_.WriteU32(cast->remote_ssrc);  // Remote SSRC.
   writer_.WriteU32(kCast);
   writer_.WriteU8(static_cast<uint8_t>(cast->ack_frame_id));
   uint8_t* cast_loss_field_pos = reinterpret_cast<uint8_t*>(writer_.ptr());
@@ -288,8 +297,7 @@ void RtcpBuilder::AddCast(const RtcpCastMessage* cast,
     }
   }
   VLOG_IF(1, !nack_string_builder.Empty())
-      << "SSRC: " << cast->media_ssrc
-      << ", ACK: " << cast->ack_frame_id
+      << "SSRC: " << cast->remote_ssrc << ", ACK: " << cast->ack_frame_id
       << ", NACK: " << nack_string_builder.GetString();
   DCHECK_LE(number_of_loss_fields, kRtcpMaxCastLossFields);
   *cast_loss_field_pos = static_cast<uint8_t>(number_of_loss_fields);