function getScaling(out, mat) {
    var m11 = mat[0];
    var m12 = mat[1];
    var m13 = mat[2];
    var m21 = mat[4];
    var m22 = mat[5];
    var m23 = mat[6];
    var m31 = mat[8];
    var m32 = mat[9];
    var m33 = mat[10];
    out[0] = Math.hypot(m11, m12, m13);
    out[1] = Math.hypot(m21, m22, m23);
    out[2] = Math.hypot(m31, m32, m33);
    return out;
  }
Returns the scaling factor component of a transformation
 matrix. If a matrix is built with fromRotationTranslationScale
 with a normalized Quaternion paramter, the returned vector will be
 the same as the scaling vector
 originally supplied.
@param  {vec3} out Vector to receive scaling factor component
@param  {ReadonlyMat4} mat Matrix to be decomposed (input)
@return {vec3} out