@shane-tomlinson @mohit-agarwal At risk of complicating this PR slightly more, I think the right approach is to modify the [include.js generation script](https://github.com/mozilla/browserid/blob/dev/scripts/create_include.js#L38-L40) to insert the type-checking functions in [common/helpers.js](https://github.com/mozilla/browserid/blob/dev/resources/static/common/js/helpers.js#L109-L123), that seems cleaner and removes duplication.

It really should be a one-liner to add that to the include-create script, shouldn't be too hairy to add.