Bug 1946105, a=dmeehan

        this._securityDelayMS = securityDelayMS;

        // Attach a global focus handler so we can restart the delay when the window

        // refocuses (e.g., user navigated away or used a popup).

        this._focusHandler = () => {

          // If the notification is still connected, restart the delay.

          if (this.isConnected) {

        this._focusHandler = event => {

          // Only restart delay if the notification is still connected and this

          // is actually a window focus.

          if (this.isConnected && event.target === window) {

            this._startClickJackingDelay();

          }

        };