Removed polymer & mirror from Observatory

runtime/observatory/lib/src/elements/helpers/nav_bar.dart

Index: runtime/observatory/lib/src/elements/helpers/nav_bar.dart
diff --git a/runtime/observatory/lib/src/elements/helpers/nav_bar.dart b/runtime/observatory/lib/src/elements/helpers/nav_bar.dart
new file mode 100644
index 0000000000000000000000000000000000000000..5c1c272704698282b31051497915408dd79033a2
--- /dev/null
+++ b/runtime/observatory/lib/src/elements/helpers/nav_bar.dart
@@ -0,0 +1,15 @@
+// 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';
+
+Element navBar(Iterable<Element> content) {
+  assert(content != null);
+  return document.createElement('nav')
+    ..classes = ['nav-bar']
+    ..children = [
+      new UListElement()
+        ..children = content,
+    ];
+}