Generate a templated Clone method for all mojo structs.

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

 // 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 %}
 {%- endfor %} {
 }
 
 {{struct.name}}::~{{struct.name}}() {
 }
-
-{%  if struct|is_cloneable_kind %}
-{{struct.name}}Ptr {{struct.name}}::Clone() const {
-  {{struct.name}}Ptr rv(New());
-{%-   for field in struct.fields %}
-{%-     if field.kind|is_object_kind and not field.kind|is_string_kind %}
-  rv->{{field.name}} = {{field.name}}.Clone();
-{%-     else %}
-  rv->{{field.name}} = {{field.name}};
-{%-     endif %}
-{%-   endfor %}
-  return rv;
-}
-{%  endif %}