A generalized stream which provides a controller for each listener.
Can be used to implement both broadcast streams and single subscription streams,
as well as any stream behavior between the two.
Change-Id: I7a75f8736ca6bc91ce266e768db68536efd24dfe
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/150936
Commit-Queue: Lasse R.H. Nielsen <lrn@google.com>
Reviewed-by: Nate Bosch <nbosch@google.com>
Lasse Reichstein Holst Nielsen