WPTs: css/css-contain/contain-html-bg-001.html css/css-contain/contain-html-bg-002.html css/css-contain/contain-html-bg-003.html The results make it pretty clear what this is about: https://wpt.fyi/analyzer?screenshot=sha1%3A93c3c4c555b8fa38035d23b475072ba6c920aaf7&screenshot=sha1%3A422ed5a9b8fce6673dbb700360cefb1ba06af8fa If <html> has a fixed size and contain: layout, the background shouldn't spread above that size.
<rdar://problem/97927457>
Created attachment 461344 [details] Patch
Created attachment 461348 [details] Patch
Committed 253031@main (320ad146e7fa): <https://commits.webkit.org/253031@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 461348 [details].