1. If an app never uses the loc_mapper then it won't get created. It's certainly easy to see that b/c split is not wired to views yet, nothing will instantiate the loc_mapper and thus the singleton won't be created. At the other end of the life cycle, once everything's migrated to split and there are no old i4x pointers anywhere, then the loc_mapper won't be instantiated and thus never injected. It's no big deal. Just a lazy loader.

1. split_migrator and get_item use the loc_mapper. They used to call the singleton fetcher, but based on @cpennington's feedback re no django dependency in xmodule, they don't any longer; however, when instantiating a split_migrator, the caller will need to call loc_mapper to get the location mapper.