Oh, no! The hard-rock dudes who called their first album ”Dirty Rotten Filthy Stinking Rich” have gotten serious! And to good effect. On its third release, Warrant envisions environmental decay (”April 2031”), and evokes, with surprising tenderness, the unhappy inner world of neglected people fixated on celebrities (”Andy Warhol Was Right”). Most impressively, the self-proclaimed dirtiest band in Hollywood sings thoughtfully (who’d have thought it?) about troubled love, especially in a brawnily touching song called ”Let It Rain.” Sure, the group’s playing can be rough. But Dog Eat Dog — with unusually compelling song-to-song segues — really rocks, and the inevitable cocky odes to sex are quite sexy. Platinum success, it seems, did something uncommon to the guys. It kept them hard — and made them think.