mojo: Adding struct's fields for python bindings

mojo/public/tools/bindings/generators/python_templates/module.py.tmpl

 {% from "module_macros.tmpl" import enum_values %}
 # Copyright 2014 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.
 
+import mojo.bindings.descriptor as _descriptor
 import mojo.bindings.reflection as _reflection
 {% if imports %}
 
 {% for import in imports %}
 import {{import.python_module}}
 {% endfor %}
 {% endif %}
 {#--- Constants #}
 {% if module.constants %}
 
@@ skipping 19 matching lines @@
 {%     endfor %}
     },
 {%   endif %}
 {%   if struct.enums %}
     'enums': {
 {%     for enum in struct.enums %}
       '{{enum|name}}': {{enum_values(enum)|indent(6)}},
 {%     endfor %}
     },
 {%   endif %}
+{%   if struct.fields %}
+    'fields': [
+{%    for byte in struct.bytes %}
+{%     for packed_field in byte.packed_fields %}
+      {{packed_field|field_descriptor}},
+{%     endfor %}
+{%   endfor %}
+    ],
+{%   endif %}
   }
 {% endfor %}