In r282686, a new "MockScrollAnimatorEnabled" web preference was added for use in tests, however it is not getting reset by the test harness between tests, resulting in spurious messages appearing in the console log of tests that happen to be run in a worker process after tests that use this setting.
Created attachment 442154 [details] Patch
Committed r284765 (243474@main): <https://commits.webkit.org/243474@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 442154 [details].
<rdar://problem/84595512>