Fix bad html library.

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index 32ec0ea00dfa8d9b7ab7319a734a2274da1c3d2d..c845b333dcfb9b57fac592062886fac3f4f61242 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -17356,7 +17356,7 @@ class Node extends EventTarget native "*Node" {
   @Creates('Null')
   var _model;
   bool _hasLocalModel;
-  StreamController<Node> _modelChangedStream;
+  Set<StreamController<Node>> _modelChangedStreams;
 
   /**
    * The data model which is inherited through the tree.
@@ -17373,7 +17373,7 @@ class Node extends EventTarget native "*Node" {
   @Experimental
   get model {
     // If we have a change handler then we've cached the model locally.
-    if (_modelChangedStream != null) {
+    if (!_modelChangedStreams.isEmpty) {
       return _model;
     }
     // Otherwise start looking up the tree.
@@ -17393,8 +17393,8 @@ class Node extends EventTarget native "*Node" {
     _ModelTreeObserver.initialize();
 
     if (changed) {
-      if (_modelChangedStream != null) {
-        _modelChangedStream.add(this);
+      if (!_modelChangedStreams.isEmpty) {
+        _modelChangedStreams.toList().forEach((stream) => stream.add(this));
       }
       // Propagate new model to all descendants.
       _ModelTreeObserver.propagateModel(this, value, false);
@@ -17423,12 +17423,11 @@ class Node extends EventTarget native "*Node" {
    * Get a stream of models, whenever the model changes.
    */
   Stream<Node> get onModelChanged {
-    if (_modelChangedStream == null) {
-      // Ensure the model is cached locally to minimize change notifications.
-      _model = model;
-      _modelChangedStream = new StreamController();
-    }
-    return _modelChangedStream.stream;
+    var result;
+    result = new StreamController(
+        onListen: () { _modelChangedStreams.add(result); },
+        onCancel: () { _modelChangedStreams.remove(result); });
+    return result;
   }
 
   /**