Optimize internals of multiplex-streams.

sdk/lib/html/dart2js/html_dart2js.dart

 /// The Dart HTML library.
 library dart.dom.html;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_collection-dev' hide Symbol;
 import 'dart:html_common';
 import 'dart:indexed_db';
 import 'dart:isolate';
 import 'dart:json' as json;
@@ skipping 26807 matching lines @@
    * Observes [path] on [object] for changes. This returns an object that can be
    * used to get the changes and get/set the value at this path.
    * See [PathObserver.values] and [PathObserver.value].
    */
   PathObserver(this.object, String path)
     : path = path, _isValid = _isPathValid(path) {
 
     // TODO(jmesserly): if the path is empty, or the object is! Observable, we
     // can optimize the PathObserver to be more lightweight.
 
-    _values = new StreamController.multiplex(onListen: _observe,
+    _values = new StreamController.broadcast(onListen: _observe,
                                              onCancel: _unobserve);
 
     if (_isValid) {
       var segments = [];
       for (var segment in path.trim().split('.')) {
         if (segment == '') continue;
         var index = int.parse(segment, onError: (_) {});
         segments.add(index != null ? index : new Symbol(segment));
       }
 
@@ skipping 2435 matching lines @@
       _position = nextPosition;
       return true;
     }
     _current = null;
     _position = _array.length;
     return false;
   }
 
   T get current => _current;
 }