AXIsolatedObject properties calculated on the main thread in getOrRetrievePropertyValue are not stored in sparse property map when empty/null, which could lead to more hits to the main thread.
<rdar://problem/116126895>
Created attachment 467902 [details] Patch
Committed 268593@main (52cc65198e64): <https://commits.webkit.org/268593@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 467902 [details].