Gin: Make it easier to implement Wrappable

gin/function_template.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "gin/function_template.h"
 
 #include "gin/per_isolate_data.h"
 
 namespace gin {
 
-WrapperInfo internal::CallbackHolderBase::kWrapperInfo = { kEmbedderNativeGin };
-
-WrapperInfo* internal::CallbackHolderBase::GetWrapperInfo() {
-  return &kWrapperInfo;
-}
+INIT_WRAPPABLE(internal::CallbackHolderBase);
 
 void InitFunctionTemplates(PerIsolateData* isolate_data) {
   if (!isolate_data->GetObjectTemplate(
           &internal::CallbackHolderBase::kWrapperInfo).IsEmpty()) {
     return;
   }
 
   v8::Handle<v8::ObjectTemplate> templ(
       v8::ObjectTemplate::New(isolate_data->isolate()));
   templ->SetInternalFieldCount(kNumberOfInternalFields);
   isolate_data->SetObjectTemplate(&internal::CallbackHolderBase::kWrapperInfo,
                                   templ);
 }
 
 }  // namespace gin