Ellise Shafer Charli XCX delivered the ultimate “Partygirl” set at Glastonbury Festival on Friday night, bringing out Robyn for a performance of “With Every Heartbeat,” as well as Romy, from indie rock band the xx, who remixed Robyn’s iconic millennial anthem “Dancing on My Own.” Charli’s latest album, “Brat,” has launched the avant-garde pop star into a whole new stratosphere with near-unanimous critical acclaim. The record, which is a celebration of rave music balanced with moments of vulnerability, debuted at the second spot on the U.K.