By winning the Kentucky Derby and the Preakness Stakes, California Chrome already has brought a big sales boost for All Pro Championships Inc. And if the Thoroughbred wins Saturday's Belmont Stakes, the merchandising company could see a windfall. Ben Erps, president of All Pro Championships, reached a merchandising deal with the owners of the Kentucky Derby winner California Chrome, Perry Martin and Steve Coburn, shortly before the horse ran in the Preakness, which is the second leg of horse racing's…