Fixing dart2js size regression introduced by Node.model.

tools/dom/templates/html/impl/impl_Node.darttemplate

 // 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.
 
 part of $LIBRARYNAME;
 
 /**
  * Lazy implementation of the child nodes of an element that does not request
  * the actual child nodes of an element until strictly necessary greatly
  * improving performance for the typical cases where it is not required.
@@ skipping 320 matching lines @@
     } else {
       for (var node in newNodes) {
         this.insertBefore(node, refChild);
       }
     }
   }
 
   // Note that this may either be the locally set model or a cached value
   // of the inherited model. This is cached to minimize model change
   // notifications.
+$if DART2JS
+  @Creates('Null')
+$endif
   var _model;
   bool _hasLocalModel;
   StreamController<Node> _modelChangedStream;
 
   /**
    * The data model which is inherited through the tree.
    *
    * Setting this will propagate the value to all descendant nodes. If the
    * model is not set on this node then it will be inherited from ancestor
    * nodes.
@@ skipping 59 matching lines @@
     if (_modelChangedStream == null) {
       // Ensure the model is cached locally to minimize change notifications.
       _model = model;
       _modelChangedStream = new StreamController.broadcast();
     }
     return _modelChangedStream.stream;
   }
 
 $!MEMBERS
 }