code: public void disable(String disabledReason) {
  
          m_enabled = false;
          // hide the current file input field
          if (m_fileInput != null) {
              m_fileInput.getElement().getStyle().setDisplay(Display.NONE);
          }
  
          updateState("up-disabled");
          super.setTitle(disabledReason);
      }
docs: Disables the button and changes the button title attribute to the disabled reason.<p>
  
  @param disabledReason the disabled reason