What was found
CRUISING AT FL280 R2 WINDOW ARCING WAS NOTICED, FOLLOWED BY CRACKING OF OUTER PANE. APPROPRIATE CHECKLIST WAS ACCOMPLISHED. FLIGHT RETURNED TO OAK DUE TO ICING CONDITIONS AT SEA, PDX, GEG. REMOVED AND REPLACED R2 WINDOW ASSY AND WINDOW HEAT CONTROLLER PER BOEING M/M AND OPS CK GOOD. CONTROLLER (P/N 83000-05602), (S/N 7670) 0FF, (S/N 3226) ON.