Fix pub errorgroup and analyzer errors.

tests/lib/async/stream_state_helper.dart

Index: tests/lib/async/stream_state_helper.dart
diff --git a/tests/lib/async/stream_state_helper.dart b/tests/lib/async/stream_state_helper.dart
index 074a8f125afb6776eef4c3f76cdc3eeb8107866a..f0727d65527709995fbc5a9ae065c3929a7533a1 100644
--- a/tests/lib/async/stream_state_helper.dart
+++ b/tests/lib/async/stream_state_helper.dart
@@ -519,11 +519,6 @@ class CancelCallbackEvent extends Event {
   String toString() => "[Cancelled]";
 }
 
-class _BroadcastEventCallback extends Event {
-  Function _action;
-  _BroadcastEventCallback();
-}
-
 class BroadcastCancelCallbackEvent extends Event {
   BroadcastCancelCallbackEvent(void action(StreamSubscription sub))
     : super.broadcast(action);