setThumbPosition_(res) {
    const position = this.getPositionForResolution_(res);
    const thumb = /** @type {HTMLElement} */ (this.element.firstElementChild);

    if (this.direction_ == Direction.HORIZONTAL) {
      thumb.style.left = this.widthLimit_ * position + 'px';
    } else {
      thumb.style.top = this.heightLimit_ * position + 'px';
    }
  }
Positions the thumb inside its container according to the given resolution.

@param {number} res The res.
@private