_updateValueOnHandleDrag(event) {
      const ctor = this.constructor;
      const newValue = ctor.getValueFromInteraction(event, this._effectiveStep, this._effectiveMin, this._effectiveMax, this.getBoundingClientRect(), this.directionStart);
      this.update(this._valueAffected, newValue, undefined);
    }
Updates UI and state when dragging a single Range Slider handle

@private