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..43adb6dfb008d625afff611fb0a7efdf9bf63b38 100644
--- a/media/cast/net/rtcp/rtcp_builder.cc
+++ b/media/cast/net/rtcp/rtcp_builder.cc
@@ -227,9 +227,19 @@ void RtcpBuilder::AddRrtr(const RtcpReceiverReferenceTimeReport* rrtr) {
   writer_.WriteU32(rrtr->ntp_fraction);
 }
 
+void RtcpBuilder::AddPli(const RtcpCastMessage* cast_message) {
+  AddRtcpHeader(kPacketTypePayloadSpecific, 1);
+  writer_.WriteU32(ssrc_);
+  writer_.WriteU32(cast_message->media_ssrc);
+}
+
 void RtcpBuilder::AddCast(const RtcpCastMessage* cast,
                           base::TimeDelta target_delay) {
   // See RTC 4585 Section 6.4 for application specific feedback messages.
+  if (cast->picture_loss_indicator) {
+    AddPli(cast);
+    return;

[miu, 2016/02/26 23:36:06]

Remove this, since you'll want to call AddPli() from BuildRtcpFromReceiver(), as
noted above.

[xjz, 2016/02/27 05:53:32]

Done.

+  }
   AddRtcpHeader(kPacketTypePayloadSpecific, 15);
   writer_.WriteU32(ssrc_);              // Add our own SSRC.
   writer_.WriteU32(cast->media_ssrc);  // Remote SSRC.