Define AbortableProgressPromise

[tzik]

We don't have the definition of AbortableProgressPromise at least linked documents.
Presumably, it's a custom Promise that has progress() in addition to then(), and has abort().

I think it's better for us to have written spec or reference for it.

[arunranga]

Yes; AbortableProgressPromise is a sticky loose end. I've been chatting on IRC with Domenic D. He's against it. He says: "Promises should be for one-and-done, non-interruptible, atomic-ish operations." So there isn't consensus on this, at least from the perspective of the Promise spec folks.

[tzik]

Well, what he said sounds plausilbe to me.

Then, I think we can:

• Use Promise here.
  AbortableProgressPromise is used for move(), read() and write() in current spec.
  We can eventually replace usage for read() and write() with Streams.
  So, AbortableProgressPromise matters only move(), which is not abortable in old spec.
• Use custom request class as IDB and Mozilla's FileHandle API do.
• Or, use Stream for all of move(), read() and write().
  whatwg/streams seems to head to a object stream rather than a byte stream.
  That sounds we can (ab)use it for move() as a stream of completion events.

WDYT?

[annevk]

We should adopt https://streams.spec.whatwg.org/ indeed. That would be a good first step.