Mojo C++ bindings: support enum validation.

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

-{%- from "enum_macros.tmpl" import is_valid_enum_def %}
-
-{#--- Enums #}
-{%- for enum in struct.enums -%}
-  {{is_valid_enum_def(enum, class_name=struct.name)}}
-{%- endfor %}
-
 // static
 {{struct.name}}Ptr {{struct.name}}::New() {
   {{struct.name}}Ptr rv;
   mojo::internal::StructHelper<{{struct.name}}>::Initialize(&rv);
   return rv;
 }
 
 {{struct.name}}::{{struct.name}}()
 {%- for field in struct.fields %}
     {% if loop.first %}:{% else %} {% endif %} {{field.name}}({{field|default_value}}){% if not loop.last %},{% endif %}
@@ skipping 22 matching lines @@
 {%-    if field.kind|is_typemapped_kind %}
 {#     TODO(rockot): Consider adding support for native equality testing. #}
   NOTREACHED() << "Equality testing not supported with typemapped fields.";
 {%-    else %}
   if (!mojo::internal::ValueTraits<{{field.kind|cpp_wrapper_type}}>::Equals(this->{{field.name}}, other.{{field.name}}))
     return false;
 {%-    endif %}
 {%-  endfor %}
   return true;
 }