The lineup for the 2015 Rockstar Energy Drink Mayhem Festival has been leaked online. The official tour poster, which has been circulating online, lists the following lineup: Slayer, King Diamond, HELLYEAH, The Devil Wears Prada, Whitechapel, Sister Sin, Thy Art Is Murder, Shattered Sun, Jungle Rot, Sworn In, Code Orange, Kissing Candice and Feed Her…