Taco Bell has been struggling against Chipotle (CMG 0.40%) for years in the Mexican fast-food market. But it's found a secret weapon, turning its tacos into giant Doritos chips. Doritos loves the exposure, and will launch a Locos Tacos chip early next month. Is this a fad, or a sustainable advantage that can save Taco Bell? Travis Hoium explores the latest moves by Taco Bell.