Fix propertyIsEnumerable on non-existent properties.
Fix propertyIsEnumerable on non-existent properties.

Also rename property attribute dictionaries to be more consistent with
spec.

google/CodeCity,NeilFraser/CodeCity,google/CodeCity,NeilFraser/CodeCity,NeilFraser/CodeCity,google/CodeCity,google/CodeCity,NeilFraser/CodeCity