In just 2 cases where JSPrincipals::codebase is used it can be reconstructed from the values stored in the associated nsJSPrincipal. In addition the patch makes nsJSprincipals to inherit both from nsIPrincipal and JSPrincipals allowing to use static_cast to convert between nsIPrincipal and JSPrincipals pointers and to drop many cases of manual JSPrincipal reference counting.