(Happy Valley, OR)  --  Authorities say they've arrested a man who's accused of walking into a Happy Valley Denny's and setting a customer on fire.  Clackamas County sheriff's deputies say 24-year-old DeShaun James Swanger was arrested last night without incident at a home on Southeast 80th.  Investigators say Swanger sat next to the 69-year-old victim Wednesday night, poured liquid on him, and set him on fire.  The man is listed in critical condition.