Fine. Tests for getter/setter inherited from generic interface.

Change-Id: I3439dc77ce4c9a3c11c0d83a9a128433d914976a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/422162
Reviewed-by: Paul Berry <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov