code: function breadcrumbPoints(d, i) {
    var points = [];
    points.push("0,0");
    points.push(b.w + ",0");
    points.push(b.w + b.t + "," + (b.h / 2));
    points.push(b.w + "," + b.h);
    points.push("0," + b.h);
    if (i > 0) { // Leftmost breadcrumb; don't include 6th vertex.
      points.push(b.t + "," + (b.h / 2));
    }
    return points.join(" ");
  }
docs: Generate a string that describes the points of a breadcrumb polygon.