Removed polymer & mirror from Observatory

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

Index: runtime/observatory/lib/src/elements/helpers/nav_menu.dart
diff --git a/runtime/observatory/lib/src/elements/helpers/nav_menu.dart b/runtime/observatory/lib/src/elements/helpers/nav_menu.dart
new file mode 100644
index 0000000000000000000000000000000000000000..1e8940e0ada4380d34dcea0de81f97b8d3a5711a
--- /dev/null
+++ b/runtime/observatory/lib/src/elements/helpers/nav_menu.dart
@@ -0,0 +1,21 @@
+// 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';
+
+navMenu(String label, {String link: '', Iterable<Element> content: const []}) {
+  assert(label != null);
+  assert(content != null);
+  assert(link != null);
+  return new LIElement()..classes = ['nav-menu']
+    ..children = [
+      new SpanElement()..classes = ['nav-menu_label']
+        ..children = [
+          new AnchorElement(href: link)
+            ..text = label,
+          new UListElement()
+            ..children = content
+        ]
+    ];
+}