code: function renderSelection() {
    if (!this.selectedItem) {
      return;
    }
    const selection = FractionalSelectionMixin.helpers.elementSelection(this);
    const itemCount = this.items ? this.items.length : 0;
    const damped = FractionalSelectionMixin.helpers.dampedSelection(selection, itemCount);
    // Use a percentage so the transform will still work if screen size changes
    // (e.g., if device orientation changes).
    const left = -damped * 100;
    const transform = 'translateX(' + left + '%)';
    this.$.slidingContainer.style.webkitTransform = transform;
    this.$.slidingContainer.style.transform = transform;
  }
docs: Note: In this routine, "this" is bound to an element instance.