This mostly just moves code around, to minimize potential behavior changes. There are some cleanups that we should try to do long term (this "have an array with n different counts" is pretty weird). But for now this should unblock people. The destination struct (nsStyleUIReset) was chosen mainly because it's small and non-inherited, and it doesn't seem like a worse place than nsStyleDisplay. Differential Revision: https://phabricator.services.mozilla.com/D144183