Front Burner Restaurants LP, parent to the Twin Peaks chain, has revoked the franchise agreement of the Waco, Texas, unit where nine people were killed in a shootout between motorcycle gangs, as well as with police, the company said Monday. Addison, Texas-based Front Burner said in a statement that the franchised casual-dining restaurant, which opened in August, had not followed advice to enhance security to prevent possible motorcycle gang violence.