Removed polymer & mirror from Observatory

runtime/observatory/tests/observatory_ui/nav/bar/element_test.dart

-// Copyright (c) 2016, 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 'dart:html';
-import 'package:unittest/unittest.dart';
-import 'package:observatory/src/elements/nav/bar.dart';
-
-main() {
-  NavBarElement.tag.ensureRegistration();
-
-  test('instantiation', () {
-    final e = new NavBarElement();
-    expect(e, isNotNull, reason: 'element correctly created');
-  });
-  test('elements created', () async {
-    final e = new NavBarElement();
-    document.body.append(e);
-    await e.onRendered.first;
-    expect(e.shadowRoot.children.length, isNonZero, reason: 'has elements');
-    expect(e.shadowRoot.querySelector('content'), isNotNull,
-                                               reason: 'has content elements');
-    e.remove();
-    await e.onRendered.first;
-    expect(e.shadowRoot.children.length, isZero, reason: 'is empty');
-  });
-}