162ff41b0e
* Pure interfaces marked `interface`. That's most public classes. * `Stream` made `mixin class`, as a proper skeleton/base implementation. * `Zone` classes made all `final`. Added some `<void>` to raw `Future` types. CoreLibraryReviewExempt: Aske is away. Tested: No functionality change, only added restrictions. Change-Id: I91d09fbcdba7d0dfdff3887bc7c9d54364c88b05 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/289221 Reviewed-by: Stephen Adams <sra@google.com> Reviewed-by: Nate Bosch <nbosch@google.com> Commit-Queue: Lasse Nielsen <lrn@google.com> Reviewed-by: Slava Egorov <vegorov@google.com>