No, it won't make it a chocolate stout, but it might make it a more chocolaty stout. If you keep the IBUs down on such a beer, it should turn out more like dark chocolate and less like coffee.
To really call something a "chocolate stout," you should add chocolate, cocoa, or cacao nibs. However, I've never found a chocolate stout that I enjoy as much as a stout that is brewed without all that junk but still tastes strongly of dark chocolate. The actual chocolate just gives some weird, unnatural flavor.
That's all a matter of personal taste, though, as many people I know enjoy the chocolate stouts (SWMBO included). Hey, they make 'em. Somebody's gotta drink 'em.