See bug 1736311 comment 9 for an example of this.

We allow animating pseudo-elements like ::-moz-progress-bar (and we
treat them like regular elements).

Ideally we should store animations for these in the parent element as
well, so they survive reframes and such. But treating them as regular
elements right now means that we do animate them, but we never update
animations for them correctly because wrapper.rs assumed them to be
non-animatable.

Since it seems reasonable to keep allowing the animations to happen,
let's just correct the update code and add a test.

Do you know what's the best way to add a test for this? It's a rather long-standing regression (from https://github.com/servo/servo/pull/17793 / bug 1367278).

So the problem is animation on ::-moz-progress-bar element keeps restyling even if the animation has been finished, right?

Then adding the case in file_restyles.hml and calling observeStyling(5) after the animation should have been finished and checking the number of the returned value of the observeStyling would be sufficient.

(In reply to Hiroyuki Ikezoe (:hiro) from comment #4)

So the problem is animation on ::-moz-progress-bar element keeps restyling even if the animation has been finished, right?

Then adding the case in file_restyles.hml and calling observeStyling(5) after the animation should have been finished and checking the number of the returned value of the observeStyling would be sufficient.

Drop my ni because hiro provided a way to test this. Thanks.

The Bugbug bot thinks this bug is a defect, but please change it back in case of error.

Set release status flags based on info from the regressing bug 1367278

https://hg.mozilla.org/mozilla-central/rev/782636a5bd81