The WPT test at imported/w3c/web-platform-tests/web-animations/interfaces/Animatable/animate-no-browsing-context.html is failing reliably, flaky or timing out.
<rdar://problem/41000163>
This still happens, but it's expected as we do not fully support mutable timelines, much like other browsers at this point (there is a feature flag for this).
We have support for mutable timelines now, but we still fail the "Replacing the timeline of an animation targetting an element in a document without a browsing context leaves it in the pending state" test because we don't have any logic that checks an element can actually be rendered to resolve its ready promise.
Pull request: https://github.com/WebKit/WebKit/pull/9872
Committed 260101@main (87f47a6461e3): <https://commits.webkit.org/260101@main> Reviewed commits have been landed. Closing PR #9872 and removing active labels.