Optimize internals of multiplex-streams.

sdk/lib/mdv_observe_impl/mdv_observe_impl.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.
 
 // This library itself is undocumented and not supported for end use.
 // Because dart:html must use some of this functionality, it has to be available
 // via a dart:* library. The public APIs are reexported via package:mdv_observe.
 // Generally we try to keep this library minimal, with utility types and
 // functions in the package.
 library dart.mdv_observe_impl;
@@ skipping 51 matching lines @@
  * When a field, property, or indexable item is changed, a derived class should
  * call [notifyPropertyChange]. See that method for an example.
  */
 abstract class ObservableMixin implements Observable {
   StreamController _multiplexController;
   List<ChangeRecord> _changes;
 
   Stream<List<ChangeRecord>> get changes {
     if (_multiplexController == null) {
       _multiplexController =
-          new StreamController<List<ChangeRecord>>.multiplex();
+          new StreamController<List<ChangeRecord>>.broadcast();
     }
     return _multiplexController.stream;
   }
 
   void _deliverChanges() {
     var changes = _changes;
     _changes = null;
     if (hasObservers && changes != null) {
       // TODO(jmesserly): make "changes" immutable
       _multiplexController.add(changes);
@@ skipping 134 matching lines @@
 /** Queues an action to happen during the [deliverChangeRecords] timeslice. */
 void queueChangeRecords(void deliverChanges()) {
   if (_deliverCallbacks == null) {
     _deliverCallbacks = new Queue<Function>();
     runAsync(deliverChangeRecords);
   }
   _deliverCallbacks.add(deliverChanges);
 }
 
 Queue _deliverCallbacks;