Fix for accessibility/table-sections.html in isolated tree mode.
<rdar://problem/91451873>
Created attachment 456988 [details] Patch
Created attachment 457045 [details] Patch
Created attachment 457047 [details] Patch
Committed r292603 (249435@main): <https://commits.webkit.org/249435@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 457047 [details].