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

mojo/public/tools/bindings/generators/cpp_templates/module.cc.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 106 matching lines @@
 {#--- Union builder definitions #}
 {%- for union in unions %}
 {%-   include "wrapper_union_class_definition.tmpl" %}
 {%- endfor %}
 
 {#--- Interface definitions #}
 {%- for interface in interfaces %}
 {%-   include "interface_definition.tmpl" %}
 {%- endfor %}
 
-{#--- Union Serialization Helpers #}
-{%- for union in unions %}
-{%-   include "union_serialization_definition.tmpl" %}
-{%- endfor %}
-
 {%- if variant %}
 }  // namespace {{variant}}
 {%- endif %}
 {%- for namespace in namespaces_as_array|reverse %}
 }  // namespace {{namespace}}
 {%- endfor %}
 
 namespace mojo {
 
 {#--- Struct Serialization Helpers -#}
 {%  for struct in structs %}
 {%-   if not struct|is_native_only_kind %}
 {%      include "struct_serialization_definition.tmpl" %}
 {%-   endif %}
 {%- endfor %}
 
+{#--- Union Serialization Helpers #}
+{%- for union in unions %}
+{%-   include "union_serialization_definition.tmpl" %}
+{%- endfor %}
+
 }  // namespace mojo
 
 
 #if defined(__clang__)
 #pragma clang diagnostic pop
 #elif defined(_MSC_VER)
 #pragma warning(pop)
 #endif