protected void cancelNotification(String platformTag, int platformId) {
        ensureOnCreateCalled();
        mNotificationManager.cancel(platformTag, platformId);
    }
Cancels a notification.
@param platformTag The notification tag, see
                   {@link NotificationManager#cancel(String, int)}.
@param platformId The notification id, see
                  {@link NotificationManager#cancel(String, int)}.
customtabs/src/android/support/customtabs/trusted/TrustedWebActivityService.java