_json.encode and decode are no longer supported with recent xulrunner,
JSON.stringify and parse can be used instead. Patch attached.

Does this patch break compatibility with any older versions of xulrunner than what you're running?

The oldest I have around is xulrunner-2.0, that works.

https://developer.mozilla.org/En/Using_native_JSON says that JSON was added in 1.9.1, FF 3.5

please make sure patches are compatible back to 1.9

Do we need 1.9.0 or is 1.9.1 ok? I have tested with 1.9.1 and that
works. 1.9.0 would need compatibility code.

Our current compatibility target is 1.9.0.x

Turns out that the old method was restored a couple days ago so we should
be ok for the moment. 

https://bugzilla.mozilla.org/show_bug.cgi?id=672063

Probably not worth to have a messy compatibility wrapper, we could
switch to the new method when we are ready to ditch 1.9.0?

okay, sounds fine.  i have a branch in the works that requires 1.9.2 or higher, so we won't be supporting
1.9.0.x forever.