checkIntFunction and checkIntFuncFunction need to be able to handle
different types of functions being passed to them. The easiest way to
achieve this is to make them generic.
Change-Id: I1afd13fa9514244a33d2ba7ace1f137f01b2f2a8
Reviewed-on: https://dart-review.googlesource.com/19284
Reviewed-by: Bob Nystrom <rnystrom@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>