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

tools/dom/templates/html/impl/impl_Element.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;
 
 // TODO(jacobr): use _Lists.dart to remove some of the duplicated
 // functionality.
 class _ChildrenElementList implements List {
   // Raw Element.
@@ skipping 144 matching lines @@
 
   void sort([int compare(Element a, Element b)]) {
     throw new UnsupportedError('TODO(jacobr): should we impl?');
   }
 
   dynamic reduce(dynamic initialValue,
       dynamic combine(dynamic previousValue, Element element)) {
     return IterableMixinWorkaround.reduce(this, initialValue, combine);
   }
 
+  dynamic fold(dynamic initialValue,
+      dynamic combine(dynamic previousValue, Element element)) {
+    return IterableMixinWorkaround.fold(this, initialValue, combine);
+  }
+
   void setRange(int start, int rangeLength, List from, [int startFrom = 0]) {
     throw new UnimplementedError();
   }
 
   void remove(Object object) {
     if (object is Element) {
       Element element = object;
       if (identical(element.parentNode, _element)) {
         _element.$dom_removeChild(element);
       }
@@ skipping 226 matching lines @@
 
   void sort([int compare(Element a, Element b)]) {
     throw new UnsupportedError('');
   }
 
   dynamic reduce(dynamic initialValue,
       dynamic combine(dynamic previousValue, Element element)) {
     return IterableMixinWorkaround.reduce(this, initialValue, combine);
   }
 
+  dynamic fold(dynamic initialValue,
+      dynamic combine(dynamic previousValue, Element element)) {
+    return IterableMixinWorkaround.fold(this, initialValue, combine);
+  }
+
   void setRange(int start, int rangeLength, List from, [int startFrom = 0]) {
     throw new UnsupportedError('');
   }
 
   void removeRange(int start, int rangeLength) {
     throw new UnsupportedError('');
   }
 
   void insertRange(int start, int rangeLength, [initialValue = null]) {
     throw new UnsupportedError('');
@@ skipping 700 matching lines @@
   const ScrollAlignment._internal(this._value);
   toString() => 'ScrollAlignment.$_value';
 
   /// Attempt to align the element to the top of the scrollable area.
   static const TOP = const ScrollAlignment._internal('TOP');
   /// Attempt to center the element in the scrollable area.
   static const CENTER = const ScrollAlignment._internal('CENTER');
   /// Attempt to align the element to the bottom of the scrollable area.
   static const BOTTOM = const ScrollAlignment._internal('BOTTOM');
 }