[webrtc-pc] RTCDataChannel.send during 'closing' state

lgrahl has just created a new issue for https://github.com/w3c/webrtc-pc:

== RTCDataChannel.send during 'closing' state ==
Let's look at the following scenario: Peer A and B have an `open` data channel. If peer A closes the channel, peer B's channel will go into the `closing` state until all pending messages of both peers have been sent. If peer B calls the `.send` method, it will throw an exception since the channel is not in the `open` state any more. But peer B has no way of knowing that unless it polls `.readyState`.

Do we need to address that with an... (I'm reluctant to say that) event?

Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/1827 using your GitHub account