See failures in https://wpt.fyi/results/css/css-values/round-mod-rem-computed.html?label=master&label=experimental&product=chrome&product=firefox&product=safari&aligned&view=interop&q=label%3Ainterop-2023-mathfunctions
<rdar://problem/113234898>
Is it similar to bug 255280 by any chance?
No, that other bug is about mixed units (producing a value like "10 px/em", like dimensional analysis). This bug is about round() etc. not accepting one percentage and one length/number value.
Pull request: https://github.com/WebKit/WebKit/pull/16823
Committed 267072@main (f452d441b023): <https://commits.webkit.org/267072@main> Reviewed commits have been landed. Closing PR #16823 and removing active labels.