| content | Text, image and tooltip the button displays. | 
| buttonNames | The list of options in the dropdown menu. | 
| callback | The callback to fire when a dropdown menu item is selected. | 
                  bool
        
          true when the user clicks the button.
      
Creates a large button that contains a regular button section and an arrow to open a dropdown menu.
        When the user selects the button section the method returns true. When the user selects the dropdown arrow a dropdown menu appears. When the user selects an item in the dropdown menu, callback is fired with the selected menu item as input.