set_background_icon_name
Description:
Updates the icon to use the icon named icon_name from the current icon theme as the base background image.
If icon_name is null, this will go back using style
information or default theming for its background image.
If this method is called and a Icon was already set as background for the icon,
icon_name will be used, i.e. the last method called between set_background_icon_name and
set_background_gicon has always priority.
Parameters:
| this | |
| icon_name |
an icon name, or null |