Replace WKProcessPoolWeakObserver (Direct) category with (direct) property attribute. As suggested by Timothy Hatcher.
Created attachment 439968 [details] Patch v1
Committed r283457 (242436@main): <https://commits.webkit.org/242436@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 439968 [details].
<rdar://problem/83803714>