The test at animations/stop-animation-on-suspend.html fails reliably on iOS with the new animation engine.
This isn't specific to iOS actually, it also fails on Mac but it was already marked as a flaky Failure for that platform so the error was not reported.
This test has always been problematic, see https://bugs.webkit.org/show_bug.cgi?id=49182.
I believe the expectations of this test to be incorrect. The test animates a transform from 0 to 400px across 400ms with a linear timing function. The test suspends animations from 100ms to 300ms with timers, and polls animations at 200ms and 400ms. At 200ms, it expects a value of 100px, which is correct since the animation is suspended and so the value at 100ms (when it was suspended) is expected.
However, the test expected the value at 400ms to be 200px, which leads me to think this test assumes that animations, when resumed, account for the time suspended and subtracts it from the page time. This is incorrect: when animations resume, they resume at the current time, no matter how long they were suspended. So the expected value should be 400px.
I will file a patch with this change in expectation.
Created attachment 390238 [details]
Comment on attachment 390238 [details]
Clearing flags on attachment: 390238
Committed r256177: <https://trac.webkit.org/changeset/256177>
All reviewed patches have been landed. Closing bug.