Minor changes to make cyclic_default_values_test,
cyclic_type_variable_test, and cyclic_typedef_test strong mode clean.
Bug:
Change-Id: Icc99b07eca07f937a18fd16968619e5cd7c8ca22
Reviewed-on: https://dart-review.googlesource.com/5341
Reviewed-by: Bob Nystrom <rnystrom@google.com>