pc.close says this about the ICE agent:

• Destroy connection's ICE Agent, abruptly ending any active ICE processing and any active streaming, and releasing any relevant resources (e.g. TURN permissions).

and that is all it says. It needs to update the ICE connection state to "closed", but do so synchronously, and without firing any events.

Except there's more to this, because said "closed" state says: "All of the RTCIceTransports are in the closed state." which implies a shutdown-sequence's worth of underlying RTCIceTransports states in need of changing. In other words:

1. sender.transport.state
2. sender.transport.transport.state (not a typo!)
3. sender.rtcpTansport.state
4. sender.rtcpTransport.transport.state
5. receiver.transport.state
6. receiver.transport.transport.state
7. receiver.rtcpTansport.state
8. receiver.rtcpTransport.transport.state

all need to become "closed" at this point, I think, for each sender and receiver from pc.getSenders() and pc.getReceivers() respectively.