IteratorSubject

I recently found myself writing some tests for code using the popular Bouncy Castle crypto library, which makes extensive use of non-generic Iterator objects in their public API. For example:
http://www.bouncycastle.org/docs/pgdocs1.5on/index.html

It felt a little boilerplatey to have to wrap each iterator with Lists.newArrayList/ImmutableList.of; it would have been nicer to have an IteratorSubject exposing much the same methods as IterableSubject.