Currently, we use app-specific hacks in install.rdf and install.js to add overlays that load app-specific JS files like DnD utils, find code, etc.. Not all the files should strictly be required (we need to write our own version of at least one of them because Toolkit doesn't include it), but as they are all JS files we can load them at run-time instead of using dodgy overlay hacks. I've got this working here, just need to adjust it a little to survive Mozilla/SeaMonkey's chrome registry and it'll be done.

James, I poked you about this a bit earlier. How are things?

Silver, I know you are not sold on this, and we probably should discuss this in a better place, but the new-chromereg .manifest format would support doing app-specific overlays in a very clean way - we still would need to look into how we can use that and still support older applications, which would need some investigation, but I'm willing to help on this if that way is an option.