Make asBroadcastStream take two callbacks.

pkg/scheduled_test/lib/src/utils.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library utils;
 
 import 'dart:async';
 
 import 'package:stack_trace/stack_trace.dart';
 
@@ skipping 119 matching lines @@
 }
 
 /// A function that can be called to cancel a [Stream] and send a done message.
 typedef void StreamCanceller();
 
 // TODO(nweiz): use a StreamSubscription when issue 9026 is fixed.
 /// Returns a wrapped version of [stream] along with a function that will cancel
 /// the wrapped stream. Unlike [StreamSubscription], this canceller will send a
 /// "done" message to the wrapped stream.
 Pair<Stream, StreamCanceller> streamWithCanceller(Stream stream) {
-  var controller = new StreamController(sync: true);
-  var controllerStream = stream.isBroadcast ?
-      controller.stream.asBroadcastStream() :
-      controller.stream;
+  var controller =
+      stream.isBroadcast ? new StreamController.broadcast(sync: true)
+                         : new StreamController(sync: true);
+  var controllerStream = controller.stream;
   var subscription = stream.listen((value) {
     if (!controller.isClosed) controller.add(value);
   }, onError: (error) {
     if (!controller.isClosed) controller.addError(error);
   }, onDone: controller.close);
   return new Pair<Stream, StreamCanceller>(controllerStream, controller.close);
 }
 
 // TODO(nweiz): remove this when issue 7787 is fixed.
 /// Creates two single-subscription [Stream]s that each emit all values and
@@ skipping 48 matching lines @@
 }
 
 /// Returns a string representation of [trace] that has the core and test frames
 /// folded together.
 String terseTraceString(StackTrace trace) {
   return new Trace.from(trace).terse.foldFrames((frame) {
     return frame.package == 'scheduled_test' || frame.package == 'unittest' ||
         frame.isCore;
   }).toString().trim();
 }