Adopt AbortController from DOM spec?

[felixfbecker]

Now that fetch is abortable and there are the globals AbortController and AbortSignal, should this proposal simply adopt that spec? For sure it wouldn't be ideal to have both AbortSignal and CancellationToken. But the sooner this could be speced outside of DOM the sooner we could get the types in Node, which means libraries and core APIs can rely on it for cancellation support

https://dom.spec.whatwg.org/#interface-abortcontroller
https://fetch.spec.whatwg.org/#dom-request-signal

[ikokostya]

See #16 and #17

[rbuckton]

AbortController/AbortSignal has a strong dependency on EventTarget.

I'm closing this issue as the proposal no longer specifies cancellation behavior. See #22 for the current thinking regarding cancellation and interoperability with AbortController/AbortSignal.