Generic metadata test.
Generic metadata test.

Change-Id: I4ce9379e32e90229efddb80f97bac88d5bdd21f8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/185583
Commit-Queue: Lasse R.H. Nielsen <80295e4ef244a07779f93eaa95d582bad8e316a5@google.com>
Reviewed-by: Erik Ernst <251bb01623bfda2cd9151e339a6e783ca432874c@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk