docs: private static void ensureSameWidgetSize(final DecoratedTabPanel panel) {
      if (!panel.isAttached()) {
        throw new IllegalArgumentException("panel not attached: " + panel);
      }
      int maxw = 0;
      int maxh = 0;
      for (final Widget widget : panel) {
        final int w = widget.getOffsetWidth();
        final int h = widget.getOffsetHeight();
        if (w > maxw) {
          maxw = w;
        }
        if (h > maxh) {
          maxh = h;
        }
      }
      if (maxw == 0 || maxh == 0) {
        throw new IllegalArgumentException("maxw=" + maxw + " maxh=" + maxh);
      }
      for (final Widget widget : panel) {
        setOffsetWidth(widget, maxw);
        setOffsetHeight(widget, maxh);
      }
    }