WebIDL Dictionaries

Does anyone know how to create WebIDL for dictionary types[1] using ReSpec? I'm trying to get something like this to generate a table of parameters:

dictionary IDBDatabaseOptionalParameters {
  DOMString keyPath = null;
  boolean autoIncrement = false;
};

Thanks in advance.

Eliot

[1] http://dev.w3.org/2006/webapi/WebIDL/#idl-dictionary