code: protected Icon getDefaultIcon(AbstractButton b) {
          SeaGlassContext context = getContext(b);
          Icon            icon    = context.getStyle().getIcon(context, getPropertyPrefix() + "icon");
  
          context.dispose();
          return icon;
      }
docs: Returns the default icon. This should NOT callback to the JComponent.
  
  @param  b AbstractButton the iocn is associated with.
  
  @return the default icon.