Test cases: all of the examples in https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Basic_animations I can reproduce it with GTK4 WebKitGTK build, but it works with `WEBKIT_NICOSIA_PAINTING_THREADS=0` or GTK3.
<rdar://problem/80588913>
Created attachment 458868 [details] Patch
Comment on attachment 458868 [details] Patch The mac-wk1 EWS failure is unrelated, FWIW.
Committed r293971 (250409@main): <https://commits.webkit.org/250409@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 458868 [details].