When I did the Modules code I added #activate and #deactivate, and #unload
(which pairs up with the existing #initialize).

These are sent to all classes that define these methods, when the
corresponding event occurs in a module (i.e.
activate/deactivate/initialize/unload). Compare this to how and when
initialize messages are sent to classes.

Per definition more or less, a module is always deactivated before being
unloaded, so most times you'd use deactivate I guess.

In your specific case, I think you would write class-side
activate/deactivate methods that de/register the class's services with the
FileList.

Henrik