iHeartRadio will fill the T-Mobile Arena on Friday and Saturday for the likes of U2, Drake, Sting and Usher. But millions more outside Las Vegas will be watching it via live streaming on CWTV.com and The CW app, or listening on 150 radio stations or the iHeartRadio app, which the festival was created to promote six years ago. The iHeart fest puts U2, Drake, Sia and Billy Idol on the same bill Friday and has Sting sharing the spotlight with Britney Spears and Ariana Grande on Saturday.