:mClassObject(nsnull)
: mClassObject(nsnull), mMembers(nsnull), mConstructor(nsnull), mDestructor(nsnull)
MOZ_DECL_CTOR_COUNTER(nsXBLProtoImpl)class nsXBLProtoImpl{public:  nsXBLProtoImpl()     :mClassObject(nsnull)   {     MOZ_COUNT_CTOR(nsXBLProtoImpl);     mMembers = nsnull;   };