The behavior previously tested here was to check that if a JSInput
element was marked as not processed, re-walking the DOM *should* have
reinitialized it. Unfortunately, this behavior is not supported by the
underlying JSChannel library. In fact, if JSChannel detects an existing
channel with the same origin and scope, it throws an uncaught exception,
leaving the DOM in a "broken" state.

JSInput will prevent duplicates from being added, as long as we don't
manually update the `data-processed` attribute. This behavior is already
being tested.