We're failing the Opera-submitted test at http://w3c-test.org/html/tests/submission/Opera/media/interfaces/TrackEvent/createEvent.html.
We fail to throw the NOT_SUPPORTED_ERR error when calling document.createEvent('TrackEvent'). I believe this is a broader WebCore issue that we don't follow the latest DOM spec that this method should only be used for legacy events. See http://dom.spec.whatwg.org/#dom-document-createevent.
http://dom.spec.whatwg.org/#dom-document-createevent says that we should be able to create any sort of supported event via this API.
Adam, I think you're misreading the algorithm. (Though I don't really understand why it's specced that way.)
Ah, yes. Thanks. That's quite different from the behavior we have currently.
Still not spec compliant.
Relevant, more general DOM testcase: http://w3c-test.org/dom/nodes/Document-createEvent.html
Corresponding Chrome bug: https://bugs.chromium.org/p/chromium/issues/detail?id=569690
Mass move bugs into the DOM component.