Layout Test imported/mozilla/css-animations/test_animation-cancel.html is a flaky failure

[Ryan Haddad]

The following layout test is flaky on iOS and macOS.

imported/mozilla/css-animations/test_animation-cancel.html

Probable cause:

The test has been flaky since it was imported as part of https://trac.webkit.org/changeset/229809/webkit. The test has failed at least once on release, but it is very flaky on debug bots.

Flakiness Dashboard:

https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=imported%2Fmozilla%2Fcss-animations%2Ftest_animation-cancel.html

--- /Volumes/Data/slave/highsierra-debug-tests-wk1/build/layout-test-results/imported/mozilla/css-animations/test_animation-cancel-expected.txt
+++ /Volumes/Data/slave/highsierra-debug-tests-wk1/build/layout-test-results/imported/mozilla/css-animations/test_animation-cancel-actual.txt
@@ -6,6 +6,6 @@
 PASS After cancelling an animation, updating animation properties doesn't make it live again 
 PASS After cancelling an animation, updating animation-play-state doesn't make it live again 
 PASS Setting animation-name to 'none' cancels the animation 
-PASS Setting display:none on an element cancel its animations 
+FAIL Setting display:none on an element cancel its animations assert_equals: expected "idle" but got "running"
 PASS Setting display:none on an ancestor element cancels animations on descendants

[Ryan Haddad]

Marked test as flaky in https://trac.webkit.org/r229976

[Antoine Quint]

This will be fixed by https://bugs.webkit.org/show_bug.cgi?id=183821.

[Antoine Quint]

Committed r232961: <https://trac.webkit.org/changeset/232961>

[Radar WebKit Bug Importer]

<rdar://problem/41252348>