Gin: Make it easier to implement Wrappable

gin/function_template.h.pump

 $$ This is a pump file for generating file templates.  Pump is a python
 $$ script that is part of the Google Test suite of utilities.  Description
 $$ can be found here:
 $$
 $$ http://code.google.com/p/googletest/wiki/PumpManual
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 #ifndef GIN_FUNCTION_TEMPLATE_H_
 #define GIN_FUNCTION_TEMPLATE_H_
 
@@ skipping 40 matching lines @@
 
 // CallbackHolder and CallbackHolderBase are used to pass a base::Callback from
 // CreateFunctionTemplate through v8 (via v8::FunctionTemplate) to 
 // DispatchToCallback, where it is invoked.
 //
 // v8::FunctionTemplate only supports passing void* as data so how do we know
 // when to delete the base::Callback? That's where CallbackHolderBase comes in.
 // It inherits from Wrappable, which delete itself when both (a) the refcount
 // via base::RefCounted has dropped to zero, and (b) there are no more
 // JavaScript references in V8.
-class CallbackHolderBase : public Wrappable {
- public:
-  virtual WrapperInfo* GetWrapperInfo() OVERRIDE;
-  static WrapperInfo kWrapperInfo;
+
+// This simple base class is used so that we can share a single object template
+// among every CallbackHolder instance.
+class CallbackHolderBase : public Wrappable<CallbackHolderBase> {
  protected:
-  virtual ~CallbackHolderBase() {}
+  ~CallbackHolderBase() {}
 };
 
 template<typename Sig>
 class CallbackHolder : public CallbackHolderBase {
  public:
   CallbackHolder(const base::Callback<Sig>& callback, int flags)
       : callback(callback), flags(flags) {}
   base::Callback<Sig> callback;
   int flags;
  private:
-  virtual ~CallbackHolder() {}
+  ~CallbackHolder() {}
 };
 
 
 // This set of templates invokes a base::Callback, converts the return type to a
 // JavaScript value, and returns that value to script via the provided
 // gin::Arguments object.
 //
 // In C++, you can declare the function foo(void), but you can't pass a void
 // expression to foo. As a result, we must specialize the case of Callbacks that
 // have the void return type.
@@ skipping 112 matching lines @@
   gin::Handle<HolderT> holder = CreateHandle(
       isolate, new HolderT(callback, callback_flags));
   return v8::FunctionTemplate::New(
       &internal::Dispatcher<Sig>::DispatchToCallback,
       ConvertToV8<internal::CallbackHolderBase*>(isolate, holder.get()));
 }
 
 }  // namespace gin
 
 #endif  // GIN_FUNCTION_TEMPLATE_H_