addTriangle_(a, b, c, aSrc, bSrc, cSrc) {
    this.triangles_.push({
      source: [aSrc, bSrc, cSrc],
      target: [a, b, c],
    });
  }
Adds triangle to the triangulation.
@param {import("../coordinate.js").Coordinate} a The target a coordinate.
@param {import("../coordinate.js").Coordinate} b The target b coordinate.
@param {import("../coordinate.js").Coordinate} c The target c coordinate.
@param {import("../coordinate.js").Coordinate} aSrc The source a coordinate.
@param {import("../coordinate.js").Coordinate} bSrc The source b coordinate.
@param {import("../coordinate.js").Coordinate} cSrc The source c coordinate.
@private