8d2bafa624
If the sender is not `null`, then we can send. No need for a flag, and assert() in the sending method. If the sender is `null`, then the sending code will not able to invoke it. Types FTW :-) Change-Id: I7d153ba014c578a73dce2eab28aceedbb8814711 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/298440 Commit-Queue: Konstantin Shcheglov <scheglov@google.com> Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>