Overview:Clint Eastwood narrates the history of Warner Bros., which opens with "You Ain't Heard Nothin' Yet (1923-35)," about the studio's first years, when its biggest star was Rin Tin Tin. Also remembered is its move into gritty fare, featuring James Cagney, Edward G. Robinson and Barbara Stanwyck, and its musicals. Included: "The Jazz Singer," "Public Enemy," "42nd Street," "Baby Face" and "Little Caesar"; interviews with Busby Berkeley, Alfred Hitchcock, Robinson and William Wellman.