/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
/**
 * Checks whether the user's browser supports passive event listeners.
 * See: https://github.com/WICG/EventListenerOptions/blob/gh-pages/explainer.md
 */
export declare function supportsPassiveEventListeners(): boolean;
/**
 * Normalizes an `AddEventListener` object to something that can be passed
 * to `addEventListener` on any browser, no matter whether it supports the
 * `options` parameter.
 * @param options Object to be normalized.
 */
export declare function normalizePassiveListenerOptions(options: AddEventListenerOptions): AddEventListenerOptions | boolean;