- peerconn的信令是通过post 消息到自己的信令线程消息来处理的
- PeerConnectionMessageHandler 是具体的处理器
- G:\CDN\rtcCli\m98\src\pc\peer_connection_message_handler.h
Machinery for handling messages posted to oneself

PeerConnectionMessageHandler 明确服务于 signaling_thread_

private:rtc::Thread*