code: public void addActionButton(final ToolbarAction action) {
  		final IButton button = new IButton();
  		button.setWidth(buttonSize);
  		button.setHeight(buttonSize);
  		button.setIconSize(buttonSize - WidgetLayout.toolbarStripHeight);
  		button.setIcon(action.getIcon());
  		button.setActionType(SelectionType.BUTTON);
  		button.addClickHandler(action);
  		button.setShowRollOver(false);
  		button.setShowFocused(false);
  		button.setTooltip(action.getTooltip());
  		button.setDisabled(action.isDisabled());
  
  		if (getMembers() != null && getMembers().length > 0) {
  			LayoutSpacer spacer = new LayoutSpacer();
  			spacer.setWidth(2);
  			super.addMember(spacer);
  		}
  		action.addToolbarActionHandler(new ToolbarActionHandler() {
  
  			public void onToolbarActionDisabled(ToolbarActionDisabledEvent event) {
  				button.setDisabled(true);
  			}
  
  			public void onToolbarActionEnabled(ToolbarActionEnabledEvent event) {
  				button.setDisabled(false);
  			}
  		});
  		super.addMember(button);
  	}
docs: Add a new action button to the toolbar. An action button is the kind of button that executes immediately when
  clicked upon. It can not be selected or deselected, it just executes every click.
  
  @param action
  The actual action to execute on click.