mojo/public/bindings/generators/cpp_templates/struct_definition

// static
$CLASS* $CLASS::New(mojo::Buffer* buf, mojo::Buffer::Destructor dtor) {
  return new (buf->Allocate(sizeof($CLASS), dtor)) $CLASS();
}

$CLASS::$CLASS() {
  _header_.num_bytes = sizeof(*this);
  _header_.num_fields = $NUM_FIELDS;
}