add comment about potential improvement to request handling

code/map_data_request.js

@@ -501,6 +501,9 @@ window.MapDataRequest.prototype.handleResponse = function (data, tiles, success)
 
     }
 
+    // TODO? check for any requested tiles in 'tiles' not being mentioned in the response - and handle as if it's a 'timeout'?
+
+
     window.runHooks('requestFinished', {success: true});
   }