Potentially because GTK doesn't support VIDEO_PRESENTATION_MODE yet. When I run this locally the <video> becomes visible on my desktop, which is very suspicious, because the test harness runs in XvFB...
Expectation updated in r271400
Created attachment 427765 [details]
Created attachment 427767 [details]
Tools/Scripts/svn-apply failed to apply attachment 427767 [details] to trunk.
Please resolve the conflicts and upload a new patch.
Committed r277080 (237383@main): <https://commits.webkit.org/237383@main>