Syncing wpt PR 28299 found new untriaged test failures in CI

Tests Affected

New Tests That Don't Pass

/css/css-contain/content-visibility/animation-display-lock.html
Animation events do not fire for a CSS animation running in a display locked subtree: FAIL (Chrome: PASS, Safari: FAIL)
Events and promises are handled normally for animations without an owning element: FAIL (Chrome: PASS, Safari: FAIL)

CI Results

Gecko CI (Treeherder)
GitHub PR Head

Notes

These updates will be on mozilla-central once bug 1701965 lands.

Note: this bug is for tracking fixing the issues and is not
owned by the wpt sync bot.

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This test is exercising content-visibility:hidden, which we don't yet implement.

Reopening; we've enabled content-visibility on Nightly but we still have a failure in this test:
https://wpt.fyi/results/css/css-contain/content-visibility/animation-display-lock.html

Our .ini file seems to have it annotated as random, specifically on linux 64-bit opt:
https://searchfox.org/mozilla-central/rev/e6a03adbf7930ae0cf131cc3274c80b2aae74e51/testing/web-platform/meta/css/css-contain/content-visibility/animation-display-lock.html.ini

 if (os == "linux") and not debug and fission and (processor == "x86_64"): [PASS, FAIL]

I'm not sure why we would only fail that in a Linux-specific way. I see the exact same test failure when I run the test in macOS Nightly, FWIW.

Note, I think "display lock" here is really talking about an element that is "skipped" from a content-visibility perspective. It looks like there's some subtlety about handling transitions and animations in such subtrees; https://drafts.csswg.org/css-contain-2/#cv-notes step 9 covers some of it. From a quick skim, it looks like style-queries are still supposed to cause animation events to be dispatched in some cases, but I'm not sure yet if the test's style-queries should be sufficient to trigger that or not.