Allow Object when doing lookups.

tests/corelib/map_contains_key_test.dart

Index: tests/corelib/map_contains_key_test.dart
diff --git a/tests/corelib/map_contains_key_test.dart b/tests/corelib/map_contains_key_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..32fd3db4c147830435328152a60fd7d338fa49d9
--- /dev/null
+++ b/tests/corelib/map_contains_key_test.dart
@@ -0,0 +1,22 @@
+// Copyright (c) 2011, 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";
+
+class A { const A(); }
+class B extends A { const B(); }
+
+main() {
+  var map1 = new Map<B, B>();
+  map1[const B()] = const B();
+  var map2 = new Map<B, B>();
+  var list = <B>[ const B() ];
+
+  var maps = [map1, map2];
+  for (var map in maps) {
+    // Test that the map accepts a key is not of the same type:
+    //   Map<B, ?>.containsValue(A)
+    Expect.isFalse(map.containsKey(new A()));
+  }
+}