function asBounds(trbl) {
  return {
    x: trbl.left,
    y: trbl.top,
    width: trbl.right - trbl.left,
    height: trbl.bottom - trbl.top
  };
}
Convert a { top, left, bottom, right } to an objects bounds.

@param {RectTRBL} trbl

@return {Rect}