Allow Object when doing lookups.

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;
 
 /**
  * Mixin that throws on the length changing operations of [List].
  *
  * Intended to mix-in on top of [ListMixin] for fixed-length lists.
@@ skipping 220 matching lines @@
 
   ListMapView(this._values);
 
   E operator[] (int key) => containsKey(key) ? _values[key] : null;
   int get length => _values.length;
 
   Iterable<E> get values => new SubListIterable<E>(_values, 0, null);
   Iterable<int> get keys => new _ListIndicesIterable(_values);
 
   bool get isEmpty => _values.isEmpty;
-  bool containsValue(E value) => _values.contains(value);
-  bool containsKey(int key) => key is int && key >= 0 && key < length;
+  bool containsValue(Object value) => _values.contains(value);
+  bool containsKey(Object key) => key is int && key >= 0 && key < length;
 
   void forEach(void f(int key, E value)) {
     int length = _values.length;
     for (int i = 0; i < length; i++) {
       f(i, _values[i]);
       if (length != _values.length) {
         throw new ConcurrentModificationError(_values);
       }
     }
   }
@@ skipping 16 matching lines @@
 }
 
 class ReversedListIterable<E> extends ListIterable<E> {
   Iterable<E> _source;
   ReversedListIterable(this._source);
 
   int get length => _source.length;
 
   E elementAt(int index) => _source.elementAt(_source.length - 1 - index);
 }