style: Move property allowance tests to PropertyId::parse_into.

It's not only more consistent (since we have a proper ParserContext there), but
also fixes a bunch of bugs where Gecko accidentally exposes and allows setting
internal state because of conversions from nsCSSPropertyID to PropertyId.

This adds the extra complexity of caring about aliases for longer, but that's
probably not a big deal in practice, since we also have PropertyDeclarationId.

MozReview-Commit-ID: C2Js8PfloxQ

components/layout_thread/lib.rs

@@ -742,7 +742,7 @@ impl LayoutThread {
             Msg::RegisterPaint(name, mut properties, painter) => {
                 debug!("Registering the painter");
                 let properties = properties.drain(..)
-                    .filter_map(|name| PropertyId::parse(&*name, None)
+                    .filter_map(|name| PropertyId::parse(&*name)
                         .ok().map(|id| (name.clone(), id)))
                     .filter(|&(_, ref id)| id.as_shorthand().is_err())
                     .collect();