Add instructions for switching to old UI for admin view

Previously, if you attempted to view an admin/* URL in PolyGerrit, it
rendered a blank page. This change adds the building blocks for an admin
section (router, element), but simply renders a message and link to
switch to the old UI (for whatever the URL entered was).

Bug: Issue 5406
Change-Id: I3fce0d0521122e317838f8d757895e4da6818b95

polygerrit-ui/app/elements/admin/gr-admin-view/gr-admin-view.html

@@ -0,0 +1,52 @@
+<!--
+Copyright (C) 2017 The Android Open Source Project
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+<link rel="import" href="../../../bower_components/polymer/polymer.html">
+
+<dom-module id="gr-admin-view">
+  <template>
+    <style>
+      main {
+        margin: 2em auto;
+        max-width: 46em;
+      }
+      h1 {
+        margin-bottom: .1em;
+      }
+      @media only screen and (max-width: 67em) {
+        main {
+          margin: 2em 0 2em 15em;
+        }
+      }
+      @media only screen and (max-width: 53em) {
+        .loading {
+          padding: 0 var(--default-horizontal-margin);
+        }
+        main {
+          margin: 2em 1em;
+        }
+    </style>
+    <main>
+      <h1>Admin</h1>
+      <section>
+        This page is not yet implemented in PolyGerrit. View it in the
+        <a id="gwtLink" href$="/?polygerrit=0#[[path]]" rel="external">
+        Old UI</a>
+      </section>
+    </main>
+  </template>
+  <script src="gr-admin-view.js"></script>
+</dom-module>

polygerrit-ui/app/elements/admin/gr-admin-view/gr-admin-view.js

@@ -0,0 +1,24 @@
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+(function() {
+  'use strict';
+
+  Polymer({
+    is: 'gr-admin-view',
+
+    properties: {
+      path: String,
+    },
+  });
+})();

polygerrit-ui/app/elements/core/gr-router/gr-router.js

@@ -91,6 +91,17 @@
       });
     });
 
+    page('/admin/(.*)', loadUser, function(data) {
+      restAPI.getLoggedIn().then(function(loggedIn) {
+        if (loggedIn) {
+          data.params.view = 'gr-admin-view';
+          app.params = data.params;
+        } else {
+          page.redirect('/login/' + encodeURIComponent(data.canonicalPath));
+        }
+      });
+    });
+
     function queryHandler(data) {
       data.params.view = 'gr-change-list-view';
       app.params = data.params;

polygerrit-ui/app/elements/gr-app.html

@@ -18,6 +18,8 @@ limitations under the License.
 <link rel="import" href="../behaviors/keyboard-shortcut-behavior/keyboard-shortcut-behavior.html">
 <link rel="import" href="../styles/app-theme.html">
 
+<link rel="import" href="./admin/gr-admin-view/gr-admin-view.html">
+
 <link rel="import" href="./core/gr-error-manager/gr-error-manager.html">
 <link rel="import" href="./core/gr-keyboard-shortcuts-dialog/gr-keyboard-shortcuts-dialog.html">
 <link rel="import" href="./core/gr-main-header/gr-main-header.html">
@@ -123,6 +125,9 @@ limitations under the License.
             on-account-detail-update="_handleAccountDetailUpdate">
         </gr-settings-view>
       </template>
+      <template is="dom-if" if="[[_showAdminView]]" restamp="true">
+        <gr-admin-view path="[[_path]]"></gr-admin-view>
+      </template>
       <div id="errorView" class="errorView" hidden>
         <div class="errorEmoji">[[_lastError.emoji]]</div>
         <div class="errorText">[[_lastError.text]]</div>

polygerrit-ui/app/elements/gr-app.js

@@ -112,6 +112,7 @@
       this.set('_showChangeView', view === 'gr-change-view');
       this.set('_showDiffView', view === 'gr-diff-view');
       this.set('_showSettingsView', view === 'gr-settings-view');
+      this.set('_showAdminView', view === 'gr-admin-view');
       if (this.params.justRegistered) {
         this.$.registration.open();
       }