Currently it's falling back on the narrow/legacy renderer's baseline computation, which happens to look okay. This should be fixed to have a proper computation. Also, because it's currently going through the legacy layout path, HTMLAttachmentElement::requestIconWithSize triggers its debug-assertion that it should only be used with a narrow/legacy attachment; in release it doesn't crash but probably does an extra unnecessary icon request.
<rdar://problem/111771870>
Pull request: https://github.com/WebKit/WebKit/pull/15558
Committed 265831@main (ee150aed9da8): <https://commits.webkit.org/265831@main> Reviewed commits have been landed. Closing PR #15558 and removing active labels.