Remove third_party/polymer from .gitignore

third_party/polymer/v1_0/components/more-routing/more-route-context-aware.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="../polymer/polymer.html">
-
-<link rel="import" href="route.html">
-<link rel="import" href="routing.html">
-
-<script>
-
-  MoreRouting.ContextAware = {
-
-    /** @override */
-    ready: function() {
-      this._makeRoutingReady();
-    },
-
-    /**
-     * Calls `routingReady`, and ensures that it is called in a top-down manner.
-     *
-     * We need to be sure that parent nodes have `routingReady` triggered before
-     * their children so that they can properly configure nested routes.
-     *
-     * Unfortunately, `ready` is sometimes bottom-up, sometimes top-down.
-     * Ideally, this wouldn't be necessary.
-     *
-     * @see https://github.com/Polymer/polymer/pull/1448
-     */
-    _makeRoutingReady: function() {
-      if (this.routingIsReady) return;
-
-      var node = this;
-      while (node = Polymer.dom(node).parentNode) {
-        if (typeof node._makeRoutingReady === 'function') break;
-      }
-      if (node) node._makeRoutingReady();
-
-      this.parentRoute = this._findParentRoute();
-      this.routingIsReady = true;
-      if (typeof this.routingReady === 'function') this.routingReady();
-    },
-
-    _findParentRoute: function() {
-      var node = this;
-      while (node) {
-        node = Polymer.dom(node).parentNode;
-        if (node && node.nodeType !== Node.ELEMENT_NODE) {
-          node = node.host;
-        }
-
-        var route = node && node.moreRouteContext;
-        if (route instanceof MoreRouting.Route) {
-          return route;
-        }
-      }
-      return null;
-    },
-
-  };
-
-</script>