export declare function setPageRestoreTime(time: number): void;
export declare function getPageRestoreTime(): number | undefined;
/**
 * To measure the way a user experienced a metric, we measure metrics relative to the time the user
 * started viewing the page. On prerendered pages, this is activationStart. On bfcache restores, this
 * is the page restore time. On all other pages this value will be zero.
 */
export declare function getZeroTime(): number;
/**
 * Most time-based metrics that LUX reports should be relative to the "zero" marker, rounded down
 * to the nearest unit so as not to report times in the future, and clamped to zero.
 */
export declare function processTimeMetric(value: number): number;
/**
 * Returns the number of milliseconds since navigationStart.
 */
export declare function msSinceNavigationStart(): number;
/**
 * Returns the number of milliseconds since the current page was initialized. For SPAs, this is the
 * time since the last LUX.init() call.
 */
export declare function msSincePageInit(): number;