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http://dom.spec.whatwg.org/#interface-event [[ Unset the stop propagation flag, stop immediate propagation flag, and canceled flag. ]] According to web-platform-tests[1], initializing an event should also unset defaultPrevented (which makes sense, since we're starting with a new event) [1]: https://github.com/w3c/web-platform-tests/blob/master/dom/events/Event-defaultPrevented.html#L41
That's what the canceled (sic) flag is. http://dom.spec.whatwg.org/#dom-event-defaultprevented
Ah, sorry, my bad. Thanks.