Some ideas that have been discussed for incoming messages:

* A single readable stream per WebSocket. Similar to https://streams.spec.whatwg.org/#example-rs-push-no-backpressure, but with streams.
* A WebSocket is represented as a stream of streams. Backpressure is applied by preventing reading a message until the previous one has been completely read or cancelled.
* Hybrid streams / events: each MessageEvent provides a stream in e.data. A new event won't be fired until the previous stream is closed.
* The onmessage handler can return a promise to indicate when it is not ready for a new message. yhirano@ says this won't work because onmessage is used in other places in the platform.
* Explicit suspend() and resume() methods.

All of these imply changes to the HTML standard.

Some ideas that have been discussed for outgoing messages:

* An onbufferempty event which fires when bufferedAmount transitions from non-zero to zero.
* send(ReadableStream)
* WebSocket exposes a writable stream. write() on the stream is equivalent to calling send(), except backpressure signals are available.
* As above, plus write(ReadableStream) permits arbitrarily large messages to be sent.

Can you tell me the reason of the priority change?

hey kenji, can you help triage and assign an estimated milestone?

Plan for now to Q1: exploration.
We'll assign Milestone and Priority based on what we learn.

sam for investigation.