This is a follow up on the revert of Ia57ed8ef4 that takes a slightly
different approach. Instead of letting the index filter by visiblity
(which is doing a post-filter using ChangeIsVisibleToPredicate) we
retrieve all results and apply the predicate by hand. This way, we can
add non-visible changes to the set of non-visible changes and block the
submit.
We could alternatively also use the PermissionBackend to filter the
list, but that would require us to do exactly the same as what is done
in ChangeIsVisibleToPredicate. Since the predicate is public and we
apply it to a list we directly obtained from the index, reusing it seems
OK.
Change-Id: I102ad38e3544d92448300a2a204fe657b344faa6
2f7e0e4b07