Captailize: File System
This leaks, you can probably create it on the stack:
Also, shouldn't you pass url.toLocalFile() instead of hardcoded /?
Works great and looks fine to me, and the code seems sensible too given that this dialog is currently implemented with a GridLayout. I'd like to see this ported to use a FormLayout at some point, which is both more semantically appropriate, and would also simplify this type of code. But that's material for another patch of course. :)
Please wait for at least one more review before landing.