src/vs/workbench/common/notifications.ts/NotificationsModel/onClose
class NotificationsModel:	private onClose(item: INotificationViewItem): void {
		const liveItem = this.findNotification(item);
		if (liveItem && liveItem !== item) {
			liveItem.close(); // item could have been replaced with another one, make sure to close the live item
		} else {
			item.close(); // otherwise just close the item that was passed in
		}
	}