Add Cast PLI support on sender side.

chrome/renderer/media/cast_ipc_dispatcher.cc

Index: chrome/renderer/media/cast_ipc_dispatcher.cc
diff --git a/chrome/renderer/media/cast_ipc_dispatcher.cc b/chrome/renderer/media/cast_ipc_dispatcher.cc
index 406bd6018d7dcbbf3d7cc8398e06f5a53f8bf809..61cdd948db11dc33fc2bccdd820a271d215ec46e 100644
--- a/chrome/renderer/media/cast_ipc_dispatcher.cc
+++ b/chrome/renderer/media/cast_ipc_dispatcher.cc
@@ -53,6 +53,7 @@ bool CastIPCDispatcher::OnMessageReceived(const IPC::Message& message) {
     IPC_MESSAGE_HANDLER(CastMsg_RawEvents, OnRawEvents)
     IPC_MESSAGE_HANDLER(CastMsg_Rtt, OnRtt)
     IPC_MESSAGE_HANDLER(CastMsg_RtcpCastMessage, OnRtcpCastMessage)
+    IPC_MESSAGE_HANDLER(CastMsg_Pli, OnReceivedPli);
     IPC_MESSAGE_HANDLER(CastMsg_ReceivedPacket, OnReceivedPacket)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
@@ -125,6 +126,16 @@ void CastIPCDispatcher::OnRtcpCastMessage(
   }
 }
 
+void CastIPCDispatcher::OnReceivedPli(int32_t channel_id, int32_t ssrc) {
+  CastTransportSenderIPC* sender = id_map_.Lookup(channel_id);
+  if (sender) {
+    sender->OnReceivedPli(ssrc);
+  } else {
+    DVLOG(1) << "CastIPCDispatcher::OnReceivedPli on non-existing "
+                "channel.";
+  }
+}
+
 void CastIPCDispatcher::OnReceivedPacket(int32_t channel_id,
                                          const media::cast::Packet& packet) {
   CastTransportSenderIPC* sender = id_map_.Lookup(channel_id);