It looks like you were exploiting the lack of proper encapsulation in JavaScript to use undocumented and unsupported APIs. The addon is already at risk of breaking at any time. We had a big red warning in the documentation saying not to do that.
This is the very problem we're trying to solve with the Addon SDK v2 - you should not have done that, we said we wouldn't support anyone doing that, and that support for such features could be removed at any time.
You'll need to find a new way to do this in the Addon SDK v2, or submit a feature request.