code: protected void adjustContentSize() {
  
          if (m_isFrame && m_isShowing) {
              if (m_buttonPanel != null) {
                  m_contentPanel.getElement().getStyle().setBottom(m_buttonPanel.getOffsetHeight() + 6, Unit.PX);
              } else {
                  m_contentPanel.getElement().getStyle().clearBottom();
              }
          }
      }
docs: Adjusts the content panel size according to the button panel height.<p>