function createDefaultStyle() {
  return {
    'fill-color': 'rgba(255,255,255,0.4)',
    'stroke-color': '#3399CC',
    'stroke-width': 1.25,
    'circle-radius': 5,
    'circle-fill-color': 'rgba(255,255,255,0.4)',
    'circle-stroke-width': 1.25,
    'circle-stroke-color': '#3399CC',
  };
}
@return {DefaultStyle} The default flat style.