Just as Public Image Ltd. marked a clean aesthetic break from the Sex Pistols' snotty punk, John Lydon and co. have ventured far away from the doomy dub-disco sound PiL forged on early classics like “Graveyard.” On 1986's “Bag,” the band is practically ready to rock arenas with its bleachers-bashing beat and Steve Vai-supplied guitar squeals; 2012's “I Must Be Dreaming” captures Lydon in the throes of a sun-dappled tropical-pop reverie.