int getIncScrollButtonHeight() {
      ScrollBarUI barUI = getUI();
      Insets insets = getInsets();
      if (barUI instanceof ButtonlessScrollBarUI) {
        return insets.top + ((ButtonlessScrollBarUI)barUI).getIncrementButtonHeight();
      }
      if (barUI instanceof BasicScrollBarUI) {
        try {
          JButton incrButtonValue = (JButton)BasicScrollBarUiButtonHolder.incrButtonField.invoke(barUI);
          LOG.assertTrue(incrButtonValue != null);
          return insets.bottom + incrButtonValue.getHeight();
        }
        catch (Throwable e) {
          throw new IllegalStateException(e);
        }
      }
      if (barUI != null && APPLE_LAF_AQUA_SCROLL_BAR_UI_CLASS.equals(barUI.getClass().getName())) {
        return insets.bottom + 30;
      }
      return insets.bottom + 15;
    }
int getIncScrollButtonHeight()