536b466be3
I also renamed a couple of existing tests, but the two tests for detecting unused mixins are the only substantive changes. Change-Id: I29001c9c1782395cd2824af6f8a25696e387bd3e Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/156845 Reviewed-by: Konstantin Shcheglov <scheglov@google.com> Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>