code: private void setScrollbarVisible(boolean visible) {
  
          if (visible) {
              getElement().getStyle().clearWidth();
              m_knob.getStyle().clearDisplay();
          } else {
              getElement().getStyle().setWidth(0, Unit.PX);
              m_knob.getStyle().setDisplay(Display.NONE);
          }
      }
docs: Sets the scroll bar visibility.<p>
  
  @param visible <code>true</code> to set the scroll bar visible