Fix generation of API documentation for arrays of objects

chrome/common/extensions/api/extension_api.json

 [
   {
     "namespace": "extension",
     "unprivileged": true,
     "types": [
       {
         "id": "MessageSender",
         "type": "object",
         "description": "An object containing information about the script context that sent a message or request.",
         "properties": {
@@ skipping 5781 matching lines @@
             "description": "A list of request types. Requests that cannot match any of the types will be filtered out.",
             "items": { "type": "string", "enum": ["main_frame", "sub_frame", "stylesheet", "script", "image", "object", "xmlhttprequest", "other"] }
           },
           "tabId": { "type": "integer", "optional": true },
           "windowId": { "type": "integer", "optional": true }
         }
       },
       {
         "id": "HttpHeaders",
         "type": "array",
-        "description": "An array of HTTP headers, in the form of name/value pairs.",
+        "description": "An array of HTTP headers. Each header is represented as a dictionary containing the keys <code>name</code> and <code>value</code>.",
         "items": {
           "type": "object",
           "properties": {
-            "name": {"type": "string"},
-            "value": {"type": "string"}
+            "name": {"type": "string", "description": "Name of the HTTP header."},
+            "value": {"type": "string", "description": "Value of the HTTP header."}
           }
         }
       },
       {
         "id": "BlockingResponse",
         "type": "object",
         "description": "Returns value for event handlers that have the 'blocking' extraInfoSpec applied. Allows the event handler to modify network requests.",
         "properties": {
           "cancel": {
             "type": "boolean",
@@ skipping 3348 matching lines @@
                   }
                 }
               }
             ]
           }
         ]
       }
     ]
   }
 ]