By Tanner Garrity The first time I listened to a Big Bootie mix was at a postgame in Santa Monica. I didn’t handle it particularly well. My sole link to the party — a buddy who had gone to bed — was firmly out of the picture, so I was soldiering on into the night with a roster of randos (or at least a roster of familiars to whom I was a rando). At one point, someone managed to pull up Soundcloud on the big screen, and pressed play on “Big Bootie Mix Vol. 17.” The mashup’s first three snippets: “Don’t You Worry Child (Instrumental)” by Swedish House Mafia ft. John Martin, “Don’t Start Now” by D…