[gin] Introduce Wrappable::GetObjectTemplate

gin/function_template.h

Index: gin/function_template.h
diff --git a/gin/function_template.h b/gin/function_template.h
index 14f6e78fe2fd7482e461dd7072ded9a31c77fe87..10dfa9dc0a82fc407e711d74b7e69877078ed058 100644
--- a/gin/function_template.h
+++ b/gin/function_template.h
@@ -62,8 +62,13 @@ struct CallbackParamTraits<const T*> {
 class GIN_EXPORT CallbackHolderBase : public Wrappable<CallbackHolderBase> {
  public:
   static WrapperInfo kWrapperInfo;
+
  protected:
   virtual ~CallbackHolderBase() {}
+
+ private:
+  friend class Wrappable<CallbackHolderBase>;
+  static v8::Local<v8::ObjectTemplate> GetObjectTemplate(v8::Isolate* isolate);
 };
 
 template<typename Sig>
@@ -331,11 +336,6 @@ struct Dispatcher<R(P1, P2, P3, P4)> {
 }  // namespace internal
 
 
-// This should be called once per-isolate to initialize the function template
-// system.
-GIN_EXPORT void InitFunctionTemplates(PerIsolateData* isolate_data);
-
-
 // CreateFunctionTemplate creates a v8::FunctionTemplate that will create
 // JavaScript functions that execute a provided C++ function or base::Callback.
 // JavaScript arguments are automatically converted via gin::Converter, as is