Add WTR::AccessibilityUIElement::attributeValueAsync to retrieve attribute values in isolated tree mode.
Created attachment 398290 [details] Patch
Created attachment 398294 [details] Patch
Committed r261081: <https://trac.webkit.org/changeset/261081> All reviewed patches have been landed. Closing bug and clearing flags on attachment 398294 [details].
<rdar://problem/62844799>