This results in iframes (and therefore AccessibilityScrollViews) not always being cleaned up.
<rdar://problem/96032479>
Created attachment 460512 [details] Patch
rdar://95566703
Created attachment 460518 [details] Patch
Committed 251924@main (fb36a8004ac8): <https://commits.webkit.org/251924@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 460518 [details].