Add task-page

appengine/swarming/elements/res/imp/common/single-page-style.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 contains the shared styles for the "single page" look, e.g. bot-page.
   To use, include this file and then
 
   <style include="single-page-style">
 
@@ skipping 65 matching lines @@
       .failed_task {
         background-color: #ffdddd;
       }
       .dead,
       .bot_died {
         background-color: #cccccc;
       }
       .exception {
         background-color: #edd2ff;
       }
-      .pending {
+      .pending_task {
         background-color: #fffc6c;
       }
 
     </style>
   </template>
 </dom-module>