LOS ANGELES (Reuters) – Pop star Justin Bieber and his girlfriend, Selena Gomez, a Disney actress and singer, have broken up, ending a relationship that made them one of Hollywood's most high-profile young couples, media reports said. Bieber, 18, and Gomez, 20, disclosed their relationship in February 2011 when they appeared together at an Oscar night party after months of rumors of their dating. E! Online late on Friday was the first to report the split, with other media outlets including US Weekly and People also saying the relationship was over. …