Comment 12 for bug 878165

> Firefox builds its menus dynamically, and AboutToShow() exists in the protocol to tell the application that its menu is opening. It's a bug not to send this signal when a menu is opening

My explanation was a bit confusing. The bug is that right now if you call AboutToShow() and immediatly after that call GetLayout() you get no content. If you call GetLayout() later then you get the content (cf my fake-menubar-widget script)

This behavior does not cause a problem with Unity because unity-panel-service calls AboutToShow() on all items at startup (cf Cédric dbus logs).