waitForDblTap_() {
    if (this.doubleTapTimeoutId_ !== undefined) {
      // double-click
      clearTimeout(this.doubleTapTimeoutId_);
      this.doubleTapTimeoutId_ = undefined;
    } else {
      this.handlingDoubleDownSequence_ = true;
      this.doubleTapTimeoutId_ = setTimeout(
        this.endInteraction_.bind(this),
        250,
      );
    }
  }
Wait the second double finger tap.
@private