Part of #34866

Spec: https://dom.spec.whatwg.org/#abortsignal

The event handler:

• onabort

Internal concept that plugs into the controller:

• signal abort
• run-the-abort-steps

Some other basic methods and attributes:

• aborted
• reason
• throwIfAborted()

Implementing these basic concepts is what I guess is the minimum required to use abort signals in fetch, streams(most tests seem to use a controller), and other dom event listners, see the various todos