config_service: add last import validation and tests

appengine/config_service/ui/src/config-ui/config-ui.html

 <!--
   Copyright 2017 The LUCI Authors. All rights reserved.
   Use of this source code is governed under the Apache License, Version 2.0
   that can be found in the LICENSE file.
 -->
 
 <link rel="import" href="../../bower_components/polymer/polymer.html">
 <link rel="import" href="../../bower_components/app-layout/app-layout.html">
 <link rel="import" href="../../bower_components/paper-search/paper-search-bar.html">
 <link rel="import" href="../../bower_components/app-route/app-location.html">
@@ skipping 75 matching lines @@
                 active="{{frontPageActive}}"></app-route>
 
     <template is="dom-if" if="[[frontPageActive]]">
       <front-page auth_headers="{{auth_headers}}"></front-page>
     </template>
 
     <template is="dom-if" if="[[serviceActive]]" restamp="true">
       <config-set category="services"
                   name="{{serviceData.serviceName}}"
                   route="{{serviceTail}}"
-                  auth_headers="{{auth_headers}}"></config-set>
+                  auth_headers="{{auth_headers}}"
+                  front-page-is-active="[[frontPageActive]]"></config-set>
     </template>
 
     <template is="dom-if" if="[[projectActive]]" restamp="true">
       <config-set category="projects"
                   name="{{projectData.projectName}}"
                   route="{{projectTail}}"
-                  auth_headers="{{auth_headers}}"></config-set>
+                  auth_headers="{{auth_headers}}"
+                  front-page-is-active="[[frontPageActive]]"></config-set>
     </template>
 
   </template>
 
   <script>
     Polymer({
       is: 'config-ui',
 
       properties: {
         client_id: {
           type: String,
           value: null
         }
       },
       
       ready: function() {
         this.async(function() {
           // If the path is blank, redirect to /
           if (!this.route.path) {
             this.set('route.path', '/');
           }
         });
       },
 
     });
   </script>
 </dom-module>