start(chart) {
    const anims = this._charts.get(chart);
    if (!anims) {
      return;
    }
    anims.running = true;
    anims.start = Date.now();
    anims.duration = anims.items.reduce((acc, cur) => Math.max(acc, cur._duration), 0);
    this._refresh();
  }
Start animating (all charts)
@param {Chart} chart