Preheat oven to 350 degrees F.Grease and flour a square baking pan. (8x8x2 inches.)In a mixing bowl, combine flour, brown sugar, cocoa, baking soda, and salt. Add water, oil, vanilla, and vinegar.Mix until smooth and pour into prepared pan.Sprinkle the top of the cake evenly with chocolate chips.Bake for 35 - 40 minutes or until a toothpick comes out clean. Cool on a wire rack.