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

runtime/lib/typeddata.dart

 // Copyright (c) 2013, 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.
 
 // patch classes for Int8List ..... Float64List and ByteData implementations.
 
 patch class Int8List {
   /* patch */ factory Int8List(int length) {
     return new _Int8Array(length);
   }
@@ skipping 294 matching lines @@
 
   String join([String separator]) {
     return IterableMixinWorkaround.join(this, separator);
   }
 
   dynamic reduce(dynamic initialValue,
                  dynamic combine(dynamic initialValue, element)) {
     return IterableMixinWorkaround.reduce(this, initialValue, combine);
   }
 
+  dynamic fold(dynamic initialValue,
+                 dynamic combine(dynamic initialValue, element)) {
+    return IterableMixinWorkaround.fold(this, initialValue, combine);
+  }
+
   Iterable where(bool f(int element)) {
     return IterableMixinWorkaround.where(this, f);
   }
 
   Iterable expand(Iterable f(int element)) {
     return IterableMixinWorkaround.expand(this, f);
   }
 
   Iterable take(int n) {
     return IterableMixinWorkaround.takeList(this, n);
@@ skipping 2756 matching lines @@
     return value;
   }
   return object;
 }
 
 
 void _throwRangeError(int index, int length) {
   String message = "$index must be in the range [0..$length)";
   throw new RangeError(message);
 }