There's no need for that. FormattingContexts are responsible to layout child content.
<rdar://problem/55344449>
Created attachment 378738 [details] Patch
Comment on attachment 378738 [details] Patch Nice
Comment on attachment 378738 [details] Patch Clearing flags on attachment: 378738 Committed r249849: <https://trac.webkit.org/changeset/249849>
All reviewed patches have been landed. Closing bug.