Steps to reproduce the problem:
1. Open the CSSWG testcase https://github.com/w3c/csswg-test/blob/master/css-transitions-2/transitioncancel-001.html in Edge.

What is the expected behavior?
The test should pass.

What went wrong?
The test failed, indicating that Edge is not firing the transitioncancel event when a transition is canceled.
(In this case, the cancellation is due to the element being made display:none; while the transition was in progress.)

Did this work before? No

Specification: https://drafts.csswg.org/css-transitions-2/#eventdef-transitionevent-transitioncancel
Chrome Bug: https://bugs.chromium.org/p/chromium/issues/detail?id=642487
Webkit Bug: https://bugs.webkit.org/show_bug.cgi?id=161535
Firefox Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1264125