function checkStable(zone) {
    if (zone._nesting == 0 && !zone.hasPendingMicrotasks && !zone.isStable) {
        try {
            zone._nesting++;
            zone.onMicrotaskEmpty.emit(null);
        }
        finally {
            zone._nesting--;
            if (!zone.hasPendingMicrotasks) {
                try {
                    zone.runOutsideAngular(() => zone.onStable.emit(null));
                }
                finally {
                    zone.isStable = true;
                }
            }
        }
    }
}