demos/demoUtils.js
function isPassive() {
    var supportsPassiveOption = false;
    try {
        addEventListener("test", null, Object.defineProperty({}, 'passive', {
            get: function () {
                supportsPassiveOption = true;
            }
        }));
    } catch(e) {}
    return supportsPassiveOption;
}
function isPassive() {
    var supportsPassiveOption = false;
    try {
        addEventListener("test", null, Object.defineProperty({}, 'passive', {
            get: function () {
                supportsPassiveOption = true;
            }
        }));
    } catch(e) {}
    return supportsPassiveOption;
}
ref https://github.com/WICG/EventListenerOptions/pull/30