Update the isolated tree in response to dynamic aria-grabbed and aria-posinset changes
<rdar://problem/93796181>
Created attachment 459693 [details] Patch
Created attachment 459738 [details] Patch
Committed r294863 (250995@main): <https://commits.webkit.org/250995@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 459738 [details].