When Accessibility is enabled, the WebContent process needs access to the preference service, since Accessibility is relying on some advanced features of the service.
rdar://problem/60202450
Created attachment 393523 [details] Patch
Created attachment 393529 [details] Patch
Comment on attachment 393529 [details] Patch r=me
Committed r258518: <https://trac.webkit.org/changeset/258518/webkit>