Add rpcexplorer to webapp hierarchy.

web/inc/rpcexplorer/test/descriptor.html

 <!--
   Copyright 2016 The Chromium Authors. All rights reserved.
   Use of this source code is governed by a BSD-style license that can be
   found in the LICENSE file.
   -->
 
 <!-- This file is generated by gen.go -->
 
 <script>
 var testDescriptor = {
@@ skipping 1174 matching lines @@
               22
             ]
           }
         ]
       },
       "syntax": "proto3"
     }
   ]
 };
 </script>