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

runtime/lib/array.dart

 // 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.
 
 
 // TODO(srdjan): Use shared array implementation.
 class _ObjectArray<E> implements List<E> {
 
   factory _ObjectArray(length) native "ObjectArray_allocate";
 
@@ skipping 100 matching lines @@
   }
 
   Iterable map(f(E element)) {
     return IterableMixinWorkaround.mapList(this, f);
   }
 
   reduce(initialValue, combine(previousValue, E element)) {
     return IterableMixinWorkaround.reduce(this, initialValue, combine);
   }
 
+  fold(initialValue, combine(previousValue, E element)) {
+    return IterableMixinWorkaround.fold(this, initialValue, combine);
+  }
+
   Iterable<E> where(bool f(E element)) {
     return IterableMixinWorkaround.where(this, f);
   }
 
   Iterable expand(Iterable f(E element)) {
     return IterableMixinWorkaround.expand(this, f);
   }
 
   Iterable<E> take(int n) {
     return IterableMixinWorkaround.takeList(this, n);
@@ skipping 223 matching lines @@
   }
 
   String join([String separator]) {
     return IterableMixinWorkaround.joinList(this, separator);
   }
 
   reduce(initialValue, combine(previousValue, E element)) {
     return IterableMixinWorkaround.reduce(this, initialValue, combine);
   }
 
+  fold(initialValue, combine(previousValue, E element)) {
+    return IterableMixinWorkaround.fold(this, initialValue, combine);
+  }
+
   Iterable<E> where(bool f(E element)) {
     return IterableMixinWorkaround.where(this, f);
   }
 
   Iterable expand(Iterable f(E element)) {
     return IterableMixinWorkaround.expand(this, f);
   }
 
   Iterable<E> take(int n) {
     return IterableMixinWorkaround.takeList(this, n);
@@ skipping 143 matching lines @@
     }
     _position = _length;
     _current = null;
     return false;
   }
 
   E get current {
     return _current;
   }
 }