Make asBroadcastStream take two callbacks.

sdk/lib/_internal/pub/lib/src/utils.dart

 // Copyright (c) 2012, 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.
 
 /// Generic utility functions. Stuff that should possibly be in core.
 library utils;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
@@ skipping 165 matching lines @@
     completer.completeError(e);
   }, onDone: () {
     completer.completeError(new StateError("No elements"));
   }, cancelOnError: true);
   return completer.future;
 }
 
 /// Returns a wrapped version of [stream] along with a [StreamSubscription] that
 /// can be used to control the wrapped stream.
 Pair<Stream, StreamSubscription> streamWithSubscription(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 subscription = stream.listen(controller.add,
       onError: controller.addError,
       onDone: controller.close);
-  return new Pair<Stream, StreamSubscription>(controllerStream, subscription);
+  return new Pair<Stream, StreamSubscription>(controller.stream, subscription);
 }
 
 // TODO(nweiz): remove this when issue 7787 is fixed.
 /// Creates two single-subscription [Stream]s that each emit all values and
 /// errors from [stream]. This is useful if [stream] is single-subscription but
 /// multiple subscribers are necessary.
 Pair<Stream, Stream> tee(Stream stream) {
   var controller1 = new StreamController(sync: true);
   var controller2 = new StreamController(sync: true);
   stream.listen((value) {
@@ skipping 299 matching lines @@
     error is FileException ||
     error is HttpException ||
     error is HttpException ||
     error is LinkException ||
     error is MimeMultipartException ||
     error is OSError ||
     error is ProcessException ||
     error is SocketException ||
     error is WebSocketException;
 }