ctypes.open(libname) takes a string or nsILocalFile argument. Once we move ctypes into js/src, that's not kosher. jorendorff suggested we could just try getting the 'persistentDescriptor' (I think?) property off the object, without needing a QI. That'd be a super easy workaround. We have to be careful about opening the library, though. The nsILocalFile implementation uses PR_LoadLibraryWithFlags() on Windows, I think. Which ended up being important.

P1, need this for 1.9.3. Let's drop nsILocalFile altogether. Probably want to provide hooks so embeddors can specify how to open a library. Gecko would just use PR_LoadLibraryWithFlags or something.

Fixed by bug 538324.