Gin: Consolidate all the Converter<Wrappable> subclasses.

gin/function_template.h.pump

Index: gin/function_template.h.pump
diff --git a/gin/function_template.h.pump b/gin/function_template.h.pump
index d3ae98ba9c86d8ae20cdc35565573edd646a4f76..23941c08287209c8eb03c2d8d92d5e6c0a57d8b0 100644
--- a/gin/function_template.h.pump
+++ b/gin/function_template.h.pump
@@ -188,14 +188,6 @@ $for ARG [[    typename CallbackParamTraits<P$(ARG)>::LocalType a$(ARG);
 void InitFunctionTemplates(PerIsolateData* isolate_data);
 
 
-// This has to be outside the internal namespace because template
-// specializations must be declared in the same namespace as the original
-// template.
-template<>
-struct Converter<internal::CallbackHolderBase*>
-    : public WrappableConverter<internal::CallbackHolderBase> {};
-
-
 // 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