Use checked item method in StyleProperties::getLayeredShorthandValue for mask-origin and mask-clip access.
Created attachment 460924 [details] Patch
Committed 252509@main (1ecea79c59bf): <https://commits.webkit.org/252509@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 460924 [details].
<rdar://problem/97081119>