appendFlatPointCoordinates(flatCoordinates, stride) {
    const extent = this.getBufferedMaxExtent();
    const tmpCoord = this.tmpCoordinate_;
    const coordinates = this.coordinates;
    let myEnd = coordinates.length;
    for (let i = 0, ii = flatCoordinates.length; i < ii; i += stride) {
      tmpCoord[0] = flatCoordinates[i];
      tmpCoord[1] = flatCoordinates[i + 1];
      if (containsCoordinate(extent, tmpCoord)) {
        coordinates[myEnd++] = tmpCoord[0];
        coordinates[myEnd++] = tmpCoord[1];
      }
    }
    return myEnd;
  }
@param {Array<number>} flatCoordinates Flat coordinates.
@param {number} stride Stride.
@protected
@return {number} My end