Remove third_party/polymer from .gitignore

third_party/polymer/v1_0/components/more-routing/more-route-template-helpers.html

-<!--
-Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
-This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
-The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
-The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
-Code distributed by Google as part of the polymer project is also
-subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
--->
-<link rel="import" href="routing.html">
-
-<script>
-(function(scope) {
-var MoreRouting = scope.MoreRouting = scope.MoreRouting || {};
-
-/**
- * Helper functions to spruce up your templates.
- *
- * @behavior
- */
-MoreRouting.TemplateHelpers = {
-
-  urlFor: function(pathOrName, params) {
-    return MoreRouting.urlFor(pathOrName, params);
-  },
-
-  isCurrentUrl: function(pathOrName, params) {
-    return MoreRouting.isCurrentUrl(pathOrName, params);
-  },
-
-};
-
-})(window);
-</script>