Mojo: more idiomatic C++ bindings

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

+size_t GetSerializedSize_(const {{struct.name}}Ptr& input) {
+  if (!input)
+    return 0;
+  size_t size = sizeof(internal::{{struct.name}}_Data);
+{%- for pf in struct.packed.packed_fields if pf.field.kind|is_object_kind %}
+  size += GetSerializedSize_(input->{{pf.field.name}});
+{%- endfor %}
+  return size;
+}
+
+void Serialize_({{struct.name}}Ptr input, mojo::internal::Buffer* buf,
+                internal::{{struct.name}}_Data** output) {
+  if (input) {
+    internal::{{struct.name}}_Data* result =
+        internal::{{struct.name}}_Data::New(buf);
+{%- for pf in struct.packed.packed_fields %}
+{%-   if pf.field.kind|is_object_kind %}
+    Serialize_(mojo::internal::Forward(input->{{pf.field.name}}), buf, &result->{{pf.field.name}}.ptr);
+{%-   elif pf.field.kind|is_handle_kind %}
+    result->{{pf.field.name}} = input->{{pf.field.name}}.release();
+{%-   else %}
+    result->{{pf.field.name}} = input->{{pf.field.name}};
+{%-   endif %}
+{%- endfor %}
+    *output = result;
+  } else {
+    *output = NULL;
+  }
+}
+
+void Deserialize_(internal::{{struct.name}}_Data* input,
+                  {{struct.name}}Ptr* output) {
+  if (input) {
+    {{struct.name}}Ptr result({{struct.name}}::New());
+{%- for pf in struct.packed.packed_fields %}
+{%-   if pf.field.kind|is_object_kind %}
+    Deserialize_(input->{{pf.field.name}}.ptr, &result->{{pf.field.name}});
+{%-   elif pf.field.kind|is_handle_kind %}
+    result->{{pf.field.name}}.reset(mojo::internal::FetchAndReset(&input->{{pf.field.name}}));
+{%-   elif pf.field.kind|is_enum_kind %}
+    result->{{pf.field.name}} = static_cast<{{pf.field.kind|cpp_wrapper_type}}>(
+      input->{{pf.field.name}});
+{%-   else %}
+    result->{{pf.field.name}} = input->{{pf.field.name}};
+{%-   endif %}
+{%- endfor %}
+    *output = result.Pass();
+  } else {
+    output->reset();
+  }
+}