Mojo C++ bindings: switch union to use the new serialization interface.

mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl

 // Copyright 2013 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.
 
 {%- if variant -%}
 {%-   set variant_path = "%s-%s"|format(module.path, variant) -%}
 {%- else -%}
 {%-   set variant_path = module.path -%}
 {%- endif -%}
 
@@ skipping 174 matching lines @@
 {%    endif %}
 {%- endfor %}
 
 {#--- Non-inlined structs #}
 {%  for struct in structs %}
 {%    if not struct|should_inline and not struct|is_native_only_kind %}
 {%      include "wrapper_class_declaration.tmpl" %}
 {%    endif %}
 {%- endfor %}
 
-{#--- Union Serialization Helpers -#}
-{%  if unions %}
-{%    for union in unions %}
-{%      include "union_serialization_declaration.tmpl" %}
-{%-   endfor %}
-{%- endif %}
-
 {%- for struct in structs %}
 {%-   for enum in struct.enums %}
 {{enum_stream_operator(enum)}}
 {{is_known_enum_value(enum)}}
 {%-   endfor %}
 {%- endfor %}
 
 {%- for interface in interfaces %}
 {%-   for enum in interface.enums %}
 {{enum_stream_operator(enum)}}
@@ skipping 10 matching lines @@
 
 namespace mojo {
 
 {#--- Struct Serialization Helpers -#}
 {%  for struct in structs %}
 {%-   if not struct|is_native_only_kind %}
 {%      include "struct_serialization_declaration.tmpl" %}
 {%-   endif %}
 {%- endfor %}
 
+{#--- Union Serialization Helpers -#}
+{%  if unions %}
+{%-   for union in unions %}
+{%      include "union_serialization_declaration.tmpl" %}
+{%-   endfor %}
+{%- endif %}
+
 }  // namespace mojo
 
 #endif  // {{header_guard}}