Painting bug with container queries

First noticed this in STP 186 on 12 January 2024. rdar://120951698 http://webkit.org/b/271040

steps to reproduce

1. navigate to this page
2. hit the back button

expected

you should see this page again.

actual

this page appears blank.

hitting Reload will cause the contents of this page to reappear.

relevant info

here is the CSS being applied:

See also this variant that doesn’t cause the bug to occur.