Mojo C++ bindings: add support for UnionTraits.

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

Index: mojo/public/tools/bindings/generators/cpp_templates/wrapper_union_class_definition.tmpl
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/wrapper_union_class_definition.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/wrapper_union_class_definition.tmpl
index 85cc4e61449732f0068d8629661b6e54813e69e8..e905904174d920db89fbd7ef087b7fb70b890929 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/wrapper_union_class_definition.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/wrapper_union_class_definition.tmpl
@@ -16,20 +16,6 @@
 }
 
 {%  for field in union.fields %}
-bool {{union.name}}::is_{{field.name}}() const {
-  return tag_ == Tag::{{field.name|upper}};
-}
-
-{{field.kind|cpp_union_getter_return_type}} {{union.name}}::get_{{field.name}}() const {
-  DCHECK(tag_ == Tag::{{field.name|upper}});
-{%    if field.kind|is_object_kind or
-         field.kind|is_any_handle_or_interface_kind %}
-  return *(data_.{{field.name}});
-{%-   else %}
-  return data_.{{field.name}};
-{%-   endif %}
-}
-
 void {{union.name}}::set_{{field.name}}({{field.kind|cpp_wrapper_param_type}} {{field.name}}) {
   SwitchActive(Tag::{{field.name|upper}});
 {%    if field.kind|is_string_kind %}