Fired when the browser stops displaying a menu: for example because the user clicked outside it or selected an item.
It is only triggered for menus that can be manipulated using the menus
API itself: this includes the context menu, the browser's tools menu, and the bookmarks menu.
This is most likely to be used in combination with the menus.onShown
and menus.refresh()
APIs: an extension can update the menu when it is shown, then undo the changes when it is hidden.
Firefox makes this event available via the contextMenus
namespace as well as the menus
namespace.