Ensure that hashCode and runtimeType work on null.

tests/corelib/null_nosuchmethod_test.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.
+
+// Test that Null's noSuchMethod can be closurized and called directly.
+
+main() {
+  var x;
+  // Non-existing method calls noSuchMethod.
+  Expect.throws(() => x.foo(),
+                (e) => e is NullPointerException);
+
+  // Calling noSuchMethod directly.
+  Expect.throws(() => x.noSuchMethod("foo", []),
+                (e) => e is NullPointerException);
+
+  // Closurizing noSuchMethod and calling it.
+  var nsm = x.noSuchMethod;
+  Expect.notEquals(null, nsm);
+  Expect.throws(() => nsm("foo", []),
+                (e) => e is NullPointerException);
+}