Known for big “featuring” credits on Top 40 hits “I Love It” by Icona Pop and “Fancy” by Iggy Azalea, the 21-year-old British singer Charlotte Aitchison – aka Charli XCX – filled up the intimate Sonos Studio in a tony area of West L.A. with her youthful energy and driving pop sounds. Backed by an all-girl trio, Charli XCX sang a sampling of songs mostly from last year’s album, True Romance and snuck in an upbeat cover of the 1964 pop confection, “I Want Candy.” Charli XCX finished with “Boom Clap” from the soundtrack to the teen summer movie cry-fest “The Fault In Our Stars,” already her first Top 40 hit as a solo artist.