code: function quadratic2cubicBezier (a, b) {
    return [
      [
        (a / 3 + (a + b) / 3 - a) / (b - a),
        (a * a / 3 + a * b * 2 / 3 - a * a) / (b * b - a * a)
      ], [
        (b / 3 + (a + b) / 3 - a) / (b - a),
        (b * b / 3 + a * b * 2 / 3 - a * a) / (b * b - a * a)
      ]
    ]
  }
docs: transfer Quadratic Bezier Curve to Cubic Bezier Curve
  
  @param  {number} a abscissa of p1
  @param  {number} b ordinate of p1
  @return {Array} parameter matrix for cubic bezier curve
  like [[p1x, p1y], [p2x, p2y]]