code: @Override
    public void applySubclassRelationship(
        final NominalTypeBuilder parent, final NominalTypeBuilder child, SubclassType type) {
      super.applySubclassRelationship(parent, child, type);
      if (type == SubclassType.INHERITS) {
        final FunctionType childCtor = child.constructor();
        child.declareConstructorProperty(
            "superClass_", parent.prototypeOrInstance(), childCtor.getSource());
        // Notice that constructor functions do not need to be covariant on the superclass.
        // So if G extends F, new G() and new F() can accept completely different argument
        // types, but G.prototype.constructor needs to be covariant on F.prototype.constructor.
        // To get around this, we just turn off type-checking on arguments and return types
        // of G.prototype.constructor.
        FunctionType qmarkCtor = childCtor.forgetParameterAndReturnTypes();
        child.declarePrototypeProperty("constructor", qmarkCtor, childCtor.getSource());
      }
    }
docs: Closure's goog.inherits adds a {@code superClass_} property to the
  subclass, and a {@code constructor} property.