Backdrop-filter should only uses the backdrop of the content behind up to the nearest backdrop-root, which isn't yet implemented.
<rdar://problem/115703346>
Pull request: https://github.com/WebKit/WebKit/pull/17898
Committed 268166@main (75e7dc79cac9): <https://commits.webkit.org/268166@main> Reviewed commits have been landed. Closing PR #17898 and removing active labels.
Reopening as this was reverted in https://bugs.webkit.org/show_bug.cgi?id=261840
Committed 268357@main (8e751933d8eb): <https://commits.webkit.org/268357@main> Reviewed commits have been landed. Closing PR #18070 and removing active labels.