Copy lib/dom tests that use dart:html to lib/html.

tests/dom/window_mangling_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.
-
-#library('WindowManglingTest');
-#import('../../lib/unittest/unittest.dart');
-#import('../../lib/unittest/html_config.dart');
-#import('dart:html', prefix: 'dom');
-
-// Defined in dom.Window.
-get navigator() => "Dummy";
-
-$eq(x, y) => false;
-$eq$(x, y) => false;
-
-main() {
-  useHtmlConfiguration();
-  var win = dom.window;
-
-  test('windowMethod', () {
-      final message = navigator;
-      final x = win.navigator;
-      Expect.notEquals(message, x);
-    });
-
-  test('windowEquals', () {
-      Expect.isFalse($eq(win, win));
-      Expect.isTrue(win == win);
-    });
-
-  test('windowEquals', () {
-      Expect.isFalse($eq$(win, win));
-      Expect.isTrue(win == win);
-    });
-}