Migrate test block 11 to Dart 2.0.

tests/corelib_2/iterable_reduce_test.dart

 // Copyright (c) 2014, 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.
 
 import "package:expect/expect.dart";
 import 'dart:collection';
 import 'dart:typed_data';
 
 class MyList extends ListBase {
   List list;
@@ skipping 185 matching lines @@
     ..[1] = 1
     ..[2] = 2
     ..[3] = 3;
   testModification(splayMap, put4, (x) => x.keys);
   splayMap = new SplayTreeMap()
     ..[1] = 1
     ..[2] = 2
     ..[3] = 3;
   testModification(splayMap, put4, (x) => x.values);
 }