Cache [WKAccessibilityWebPageObject accessibilityParameterizedAttributeNames] to avoid hitting often the main thread in isolated tree mode.
Created attachment 394960 [details] Patch
Committed r259253: <https://trac.webkit.org/changeset/259253> All reviewed patches have been landed. Closing bug and clearing flags on attachment 394960 [details].
<rdar://problem/61082292>