Add link to old ui back in

appengine/swarming/ui/res/imp/common/swarming-app.html

 <!--
   Copyright 2016 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.
 
   This in an HTML Import-able file that contains the definition
   of the following elements:
 
     <swarming-app>
 
@@ skipping 131 matching lines @@
               on-tap="_toggleMobileMenu"
               hidden$="[[wide_layout]]">
           </paper-icon-button>
           <div class="title left">[[name]]</div>
           <paper-spinner-lite class="left" active="[[_or(busy,_busy1,_busy2)]]"></paper-spinner-lite>
 
           <a class="left" href="/" hidden$="[[!wide_layout]]">Home</a>
           <a class="left" href="/botlist" hidden$="[[!wide_layout]]">Bot List</a>
           <a class="left" href="/tasklist" hidden$="[[!wide_layout]]">Task List</a>
           <div class="flex" hidden$="[[!wide_layout]]"></div>
+          <a class="small right" href$="[[_getOldURL()]]" hidden$="[[!wide_layout]]">Old UI</a>
           <template is="dom-if" if="[[client_id]]">
             <div class="small right">
               Server:
               <a href$="[[_versionLink(server_details)]]">
                 [[server_details.server_version]]
               </a>
             </div>
             <auth-signin
                 class="right"
                 client_id="[[client_id]]"
@@ skipping 74 matching lines @@
           type: Boolean,
           value: false,
         },
         _busy2: {
           type: Boolean,
           value: false,
         }
 
       },
 
+      _getOldURL: function() {
+        // TODO(kjlubick): Remove this on Jan 1, 2017, along with the rest
+        // of the stuff.
+        var path = window.location.pathname;
+        if (path === "/botlist") {
+          return "/oldui/restricted/bots";
+        }
+        if (path === "/tasklist") {
+          return "/oldui/user/tasks";
+        }
+        var idRegex = new RegExp("id=([^&]+)");
+        var match = idRegex.exec(window.location.search);
+        var id = "";
+        if (match && match.length > 1) {
+          id = match[1];
+        }
+        if (path === "/bot") {
+          return "/oldui/restricted/bot/" + id;
+        }
+        if (path === "/task") {
+          return "/oldui/user/task/"+id;
+        }
+
+        return "/oldui";
+      },
+
       _load: function() {
         this._getJsonAsync("permissions", "/api/swarming/v1/server/permissions",
           "_busy1", this.auth_headers);
         this._getJsonAsync("server_details", "/api/swarming/v1/server/details",
           "_busy2", this.auth_headers).catch(function(r){
             sk.errorMessage("Http response: "+ (r.status || " ") + " " + r.response);
           });
       },
 
       _toggleMobileMenu: function() {
@@ skipping 107 matching lines @@
         border: none;
         line-height: 20px;
         vertical-align: middle;
       }
 
       select {
         overflow-y: auto;
       }
   </style>
 </dom-module>