My taste buds were thrilled and my waistline was terrified when I discovered that there would be a branch of the famous D.C. diner opening in Arlington, on my side of the Potomac. How would I resist the thick, spicy half-smokes smothered in Ben's chili when I no longer had close-to-impossible parking or a two-train Metro ride separating me from them? When I visited the restaurant at 1725 Wilson Boulevard in Clarendon a few weeks ago, it was even worse than I feared.