Add Iterable.fold (and Stream.fold) which replace `reduce`.

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 132 matching lines @@
   // looking up the nodeList only once instead of once per iteration.
   bool contains(Node element) => IterableMixinWorkaround.contains(this, element);
 
   void forEach(void f(Node element)) => IterableMixinWorkaround.forEach(this, f);
 
   dynamic reduce(dynamic initialValue,
       dynamic combine(dynamic previousValue, Node element)) {
     return IterableMixinWorkaround.reduce(this, initialValue, combine);
   }
 
+  dynamic fold(dynamic initialValue,
+      dynamic combine(dynamic previousValue, Node element)) {
+    return IterableMixinWorkaround.fold(this, initialValue, combine);
+  }
+
   String join([String separator]) {
     return IterableMixinWorkaround.joinList(this, separator);
   }
 
   Iterable map(f(Node element)) {
     return IterableMixinWorkaround.mapList(this, f);
   }
 
   Iterable<Node> where(bool f(Node element)) {
     return IterableMixinWorkaround.where(this, f);
@@ skipping 245 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
 }