groupLabelRect(groupIndex) {
        if (this.labelsOnTop) {
            let r = this.gateDrawRect(groupIndex, 0);
            let c = new Point(r.x + Config.TOOLBOX_GATE_SPAN - Config.TOOLBOX_GATE_SPACING / 2, r.y - 18);
            return new Rect(c.x - Config.TOOLBOX_GATE_SPAN, c.y, Config.TOOLBOX_GATE_SPAN * 2, 20);
        }

        let r = this.gateDrawRect(groupIndex, this.groupHeight*2 - 2);
        let c = new Point(r.x + Config.TOOLBOX_GATE_SPAN - Config.TOOLBOX_GATE_SPACING / 2, r.bottom());
        return new Rect(c.x - Config.TOOLBOX_GATE_SPAN, c.y+2, Config.TOOLBOX_GATE_SPAN * 2, 20);
    }
@param {!int} groupIndex
@returns {!Rect}
@private