StateChange
- offer = pc.CreateOffer()
- pc.SetLocalDescription(offer)
- OnICEGatheringStateChange: gathering
- OnSignalingStateChange: have-local-offer
*. OnICEGatheringStateChange: complete
- pc.SetRemoteDescription(answer)
- OnSignalingStateChange: stable
- OnICEConnectionStateChange: checking
- OnICEConnectionStateChange: connected