Preheat oven to 350ºF. In a dry skillet over medium heat, toast the coconut for about 5 minutes, stirring constantly until light golden-brown. Do not burn. Coat a 9″ x 13″ pan with cooking spray. Spread the toasted coconut and walnuts evenly in the bottom of the pan. In a mixing bowl, combine dry cake mix, eggs, water, and oil, and mix until well blended. Pour the batter over the coconut and nuts. In another bowl, mix together the cream cheese, butter, vanilla, and powdered sugar until light and fluffy. Spread the mixture in dollops over the batter. Sprinkle with chocolate chips. Bake for 40-45 minutes or until the cake has set.