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

sdk/lib/_collection_dev/list.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.
 
 part of dart._collection.dev;
 
 /**
  * Base implementation of a [List] class.
  *
  * This class can be used as a mixin.
@@ skipping 189 matching lines @@
       }
       return buffer.toString();
     }
   }
 
   Iterable<E> where(bool test(E element)) => new WhereIterable<E>(this, test);
 
   Iterable map(f(E element)) => new MappedListIterable(this, f);
 
   reduce(var initialValue, combine(var previousValue, E element)) {
+    return fold(initialValue, combine);
+  }
+
+  fold(var initialValue, combine(var previousValue, E element)) {
     var value = initialValue;
     int length = this.length;
     for (int i = 0; i < length; i++) {
       value = combine(value, this[i]);
       if (length != this.length) {
         throw new ConcurrentModificationError(this);
       }
     }
     return value;
   }
@@ skipping 503 matching lines @@
   }
 
   E remove(int key) {
     throw new UnsupportedError("Cannot modify an unmodifiable map");
   }
 
   void clear() {
     throw new UnsupportedError("Cannot modify an unmodifiable map");
   }
 }