These tests were added in r286743 and test the layout of captions on a video. They have failed on both GTK and WPE since they were added.
Created attachment 447515 [details] Patch
Created attachment 447516 [details] Patch
Committed r287239 (245399@main): <https://commits.webkit.org/245399@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 447516 [details].
<rdar://problem/86680839>