it's guaranteed to have a parent (unless it's the ICB).
<rdar://problem/60742432>
Created attachment 394215 [details] Patch
Created attachment 394237 [details] Patch
Created attachment 394843 [details] Patch
Committed r259180: <https://trac.webkit.org/changeset/259180> All reviewed patches have been landed. Closing bug and clearing flags on attachment 394843 [details].