code: @SuppressWarnings("WeakerAccess")
    public SnackbarBuilder dismissCallback(final SnackbarDismissCallback callback) {
      callbacks.add(new SnackbarCallback() {
        public void onSnackbarDismissed(Snackbar snackbar, int dismissEvent) {
          callback.onSnackbarDismissed(snackbar, dismissEvent);
        }
      });
      return this;
    }
docs: Set the callback to be informed of the Snackbar being dismissed through some means.
  
  @param callback The callback.
  @return This instance.