Dynamically generate a heading for Extension Docs API pages

chrome/common/extensions/api/top_sites.json

 // Copyright (c) 2012 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.
 
 [
   {
     "namespace": "topSites",
+    "description": "The top sites module allows access to the top sites that are displayed on the new tab page.",
     "types": [
       {
         "id": "MostVisitedURL",
         "type": "object",
         "description": "An object encapsulating a most visited URL, such as the URLs on the new tab page.",
         "properties": {
           "url": {"type": "string", "description": "The most visited URL."},
           "title": {"type": "string", "description": "The title of the page"}
         }
       }
@@ skipping 13 matching lines @@
                 "name": "data",
                 "items": {"$ref": "MostVisitedURL"}
               }
             ]
           }
         ]
       }
     ]
   }
 ]