It was badly converted to Dart 2, and was both using and testing things
that can no longer happen (like returning a non-null non-String value
from toString).
Change-Id: I085d1172f177e80c3f75af36a2028b7ea241713a
Reviewed-on: https://dart-review.googlesource.com/71144
Reviewed-by: Kevin Millikin <kmillikin@google.com>
Commit-Queue: Lasse R.H. Nielsen <lrn@google.com>