Make the fuchsia mojo/public repo the source of truth.

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

-{%- set class_name = struct.name ~ "_Data" -%}
-
-class {{class_name}} {
- public:
-  static {{class_name}}* New(mojo::internal::Buffer* buf);
-
-  static mojo::internal::ValidationError Validate(
-      const void* data,
-      mojo::internal::BoundsChecker* bounds_checker,
-      std::string* err);
-
-  void EncodePointersAndHandles(std::vector<mojo::Handle>* handles);
-  void DecodePointersAndHandles(std::vector<mojo::Handle>* handles);
-
-  mojo::internal::StructHeader header_;
-{%- for packed_field in struct.packed.packed_fields %}
-{%-   set name = packed_field.field.name %}
-{%-   set kind = packed_field.field.kind %}
-{%-   if kind.spec == 'b' %}
-  uint8_t {{name}} : 1;
-{%-   elif kind|is_enum_kind %}
-  int32_t {{name}};
-{%-   else %}
-  {{kind|cpp_field_type}} {{name}};
-{%-   endif %}
-{%-   if not loop.last %}
-{%-     set next_pf = struct.packed.packed_fields[loop.index0 + 1] %}
-{%-     set pad = next_pf.offset - (packed_field.offset + packed_field.size) %}
-{%-     if pad > 0 %}
-  uint8_t pad{{loop.index0}}_[{{pad}}];
-{%-     endif %}
-{%-   endif %}
-{%- endfor %}
-
-{%- set num_fields = struct.versions[-1].num_fields %}
-{%- if num_fields > 0 %}
-{%-   set last_field = struct.packed.packed_fields[num_fields - 1] %}
-{%-   set offset = last_field.offset + last_field.size %}
-{%-   set pad = offset|get_pad(8) %}
-{%-   if pad > 0 %}
-  uint8_t padfinal_[{{pad}}];
-{%-   endif %}
-{%- endif %}
-
- private:
-  {{class_name}}();
-  ~{{class_name}}() = delete;
-};
-static_assert(sizeof({{class_name}}) == {{struct.versions[-1].num_bytes}},
-              "Bad sizeof({{class_name}})");