getLength() {
    const ends = this.ends_;
    let start = 0;
    let length = 0;
    for (let i = 0, ii = ends.length; i < ii; ++i) {
      length += lineStringLength(
        this.flatCoordinates,
        start,
        ends[i],
        this.stride,
      );
      start = ends[i];
    }
    return length;
  }
Return the sum of all line string lengths
@return {number} Length (on projected plane).
@api