How to use the webvr-polyfill/src/util.isFirefoxAndroid function in webvr-polyfill

super();

		this.deviceMotion = new DeviceMotion();

		this.accelerometer = new MathUtil.Vector3();
		this.gyroscope = new MathUtil.Vector3();

		this._onDeviceMotionChange = this._onDeviceMotionChange.bind(this);
		this._onScreenOrientationChange = this._onScreenOrientationChange.bind(this);

		this.filter = new ComplementaryFilter(K_FILTER);
		this.posePredictor = new PosePredictor(PREDICTION_TIME_S);

		this.filterToWorldQ = new MathUtil.Quaternion();

		this.isFirefoxAndroid = Util.isFirefoxAndroid();
		this.isIOS = Util.isIOS();

		// Ref https://github.com/immersive-web/cardboard-vr-display/issues/18
		this.isChromeUsingDegrees = agentInfo.browser.name === "chrome" &&
			parseInt(agentInfo.browser.version, 10) >= 66;

		this._isEnabled = false;

		// Set the filter to world transform, depending on OS.
		if (this.isIOS) {
			this.filterToWorldQ.setFromAxisAngle(new MathUtil.Vector3(1, 0, 0), Math.PI / 2);
		} else {
			this.filterToWorldQ.setFromAxisAngle(new MathUtil.Vector3(1, 0, 0), -Math.PI / 2);
		}

		this.inverseWorldToScreenQ = new MathUtil.Quaternion();