We do not currently account for iterationComposite when interpolating custom properties.
Pull request: https://github.com/WebKit/WebKit/pull/7690
Committed 257925@main (f391c2f826f2): <https://commits.webkit.org/257925@main> Reviewed commits have been landed. Closing PR #7690 and removing active labels.
<rdar://problem/103405359>