Specs say "if [[Class]] is <foo>" a bunch of places, and probably in that case both wrapped and unwrapped objects should pass. The isFoo() methods on JSObject don't unwrap, and it seems to me they shouldn't -- we should keep wrappy-ness separate from that. So we should have something that first tries the unwrapped check, then the wrapped check. But it should be separate from the isFoo() methods, because in some situations the isFoo() check is really a guard on a fast-path for direct slot access, or whatever, and I don't think we should throw that out or make everything check-then-recheck.

Compartment-per-global will need this since a lot more content will be running up against these discrepancies.