code: private Path getBottomLeftoverPath(int width, int height) {
          int hw = width / 2, hh = height / 2;
          int c = cornerSize;
          Path p = new Path();
          p.moveTo((c > hw ? hw : c), (c > hh ? hh : c));
          p.lineTo(width - (c > hw ? hw : c), (c > hh ? hh : c));
          p.lineTo(width - (c > hw ? hw : c), height);
          p.lineTo((c > hw ? hw : c), height);
          p.close();
          return p;
      }
docs: 获取底部除去左右边角部分之后剩余的部分填充