d2a37231b3
Refactors async* implementation class to dart:async and ports it back to Dart. Improves `await` to avoid zone registration at each await. Change-Id: I15cac2a40bd56269c8ade1dc0810792c23459ef5 Reviewed-on: https://dart-review.googlesource.com/59260 Commit-Queue: Jenny Messerly <jmesserly@google.com> Reviewed-by: Bob Nystrom <rnystrom@google.com> Reviewed-by: Vijay Menon <vsm@google.com>