[mojo-bindings] Support reuse of native enum classes

mojo/public/tools/bindings/generators/cpp_templates/struct_serialization_declaration.tmpl

 size_t GetSerializedSize_(const {{struct.name}}Ptr& input);
 void Serialize_({{struct.name}}Ptr input, mojo::internal::Buffer* buffer,
                 internal::{{struct.name}}_Data** output);
 bool Deserialize_(internal::{{struct.name}}_Data* input,
                   {{struct.name}}Ptr* output,
                   mojo::internal::SerializationContext* context);
 
-{%- if struct|is_native_only_kind and struct|is_typemapped_kind %}
+{%- if struct|is_native_struct_kind and struct|is_typemapped_kind %}
 {# This helps the array serializer understand how to serialize arrays of this
    native-only type. #}
 
 {%-   for namespace in namespaces_as_array|reverse %}
 }  // namespace {{namespace}}
 {%-   endfor %}
 {%-   if variant %}
 }  // namespace {{variant}}
 {%-   endif %}
 
@@ skipping 91 matching lines @@
 
   static bool Deserialize(internal::{{struct.name}}_Data* input,
                           NativeType* output,
                           mojo::internal::SerializationContext* context) {
     return mojo::StructTraits<{{struct.name}}, NativeType>::Read(
         {{struct.name}}_Reader(input, context), output);
   }
 };
 
 {%- endif %}  {# not variant #}