webrtc代码走读：发送端NACK和FEC的packet压到队列走读

一、NACK发送端packet data和FEC的packet data push到packet队列函数调用栈

PacingController::ProcessPackets()
->PacketRouter::SendPacket(std::unique_ptr,const PacedPacketInfo&)
->ModuleRtpRtcpImpl2::TrySendPacket(RtpPacketToSend*, const PacedPacketInfo&) 
->RtpSenderEgress::SendPacket(RtpPacketToSend*, const PacedPacketInfo&) 

RtpSenderEgress::SendPacket函数压栈packet到NACK和FEC队列 

FEC压栈队列 

NACK压栈队列 

保存packet