A LegendEvent is passed to
LegendControl.onOverlayToggled() once an overlayToggled event 
fires. It contains the name of the overlay that was toggled and whether
it was turned on or off.
                                                
                    
| Method Attributes | Method Name and Description | 
|---|---|
| 
                                        
                                         Returns the overlay name for the event. 
                                     | 
                                |
| 
                                        
                                         Returns the visibility state for the overlay for the event. 
                                     |