Add the c++ code part of bindings2/

sky/engine/bindings2/scripts/templates/attributes_cpp.template

 {##############################################################################}
 {% macro attribute_getter(cpp_class, attribute) %}
 static void {{static_attribute_name(attribute, 'Getter')}}(Dart_NativeArguments args) {
 {% if attribute.is_getter_raises_exception or attribute.is_call_with_execution_context %}
     Dart_Handle exception = nullptr;
 {% endif %}
   {
 {% if attribute.is_call_with_execution_context %}
     ExecutionContext* context = DOMDartState::CurrentDocument();
     if (!context) {
-      exception = Dart_NewStringFromCString("Failed to retrieve a context");
+      exception = ToDart("Failed to retrieve a context");
       goto fail;
     }
 {% endif %}
 {% if attribute.is_call_with_script_state %}
     DartState* dart_state = DartState::Current();
     DCHECK(state);
 {% endif %}
 {% if attribute.dart_set_return_value and not attribute.is_static %}
     {{cpp_class}}* receiver = GetReceiver<{{cpp_class}}>(args);
 {% else %}
@@ skipping 66 matching lines @@
 {% set attribute_name = attribute.name if not attribute.put_forwards else 'value' %}
 
         {{attribute.local_cpp_type}} {{attribute.setter_lvalue}} = {{attribute.dart_value_to_local_cpp_value}};
         if (exception)
             goto fail;
 {% if attribute.is_call_with_execution_context or
       attribute.is_setter_call_with_execution_context %}
 
         ExecutionContext* context = DOMDartState::CurrentDocument();
         if (!context) {
-            exception = Dart_NewStringFromCString("Failed to retrieve a context");
+            exception = ToDart("Failed to retrieve a context");
             goto fail;
         }
 
 {% endif %}
 
 {% if attribute.is_call_with_script_state %}
         ScriptState* state = DartUtilities::currentScriptState();
         if (!state) {
-            exception = Dart_NewStringFromCString("Failed to retrieve a script state");
+            exception = ToDart("Failed to retrieve a script state");
             goto fail;
         }
 {% endif %}
 {% if attribute.is_setter_raises_exception %}
         ExceptionState es;
 {% endif %}
         {{attribute.cpp_setter}};
 {% if attribute.is_setter_raises_exception %}
         if (es.had_exception()) {
             exception = es.GetDartException(args, {{attribute.auto_scope}});
@@ skipping 77 matching lines @@
 {% macro generate_attribute_symbolizer_body(dart_class, class_name, attribute) %}
 if (native_function == {{dart_class}}Internal::{{static_attribute_name(attribute, 'Getter')}}) {
     return reinterpret_cast<const uint8_t*>("{{attribute.native_entry_getter.resolver_string}}");
 }
   {% if not attribute.is_read_only %}
 if (native_function == {{dart_class}}Internal::{{static_attribute_name(attribute, 'Setter')}}) {
     return reinterpret_cast<const uint8_t*>("{{attribute.native_entry_setter.resolver_string}}");
 }
   {% endif %}
 {% endmacro %}