code: function reducePath(contour) {
  
              if (!contour.length) {
                  return contour;
              }
  
              var prev;
              var next;
              var p;
              for (var i = contour.length - 1, last = i; i >= 0; i--) {
  
                  // 这里注意逆序
                  p = contour[i];
                  next = i === last ? contour[0] : contour[i + 1];
                  prev = i === 0 ? contour[last] : contour[i - 1];
  
                  if (redundant(prev, p, next)) {
                      contour.splice(i, 1);
                      last--;
                      continue;
                  }
              }
  
              return contour;
          }
docs: 缩减glyf，去除冗余节点
  
  @param {Array} contour 路径对象
  @return {Array} 路径对象