Provide private symbols through internal APIs

src/api.h

Index: src/api.h
diff --git a/src/api.h b/src/api.h
index 9197bafbc52331785f8d636b732a68e61281ba47..7b35697c959fa0e5a4f93babbd59d1694494e88a 100644
--- a/src/api.h
+++ b/src/api.h
@@ -184,6 +184,7 @@ class RegisteredExtension {
   V(DataView, JSDataView)                      \
   V(String, String)                            \
   V(Symbol, Symbol)                            \
+  V(Private, Private)                          \
   V(Script, Object)                            \
   V(Function, JSFunction)                      \
   V(Message, JSObject)                         \
@@ -211,6 +212,8 @@ class Utils {
       v8::internal::Handle<v8::internal::String> obj);
   static inline Local<Symbol> ToLocal(
       v8::internal::Handle<v8::internal::Symbol> obj);
+  static inline Local<Private> ToLocal(
+      v8::internal::Handle<v8::internal::Private> obj);
   static inline Local<RegExp> ToLocal(
       v8::internal::Handle<v8::internal::JSRegExp> obj);
   static inline Local<Object> ToLocal(
@@ -350,6 +353,7 @@ MAKE_TO_LOCAL(ToLocal, Object, Value)
 MAKE_TO_LOCAL(ToLocal, JSFunction, Function)
 MAKE_TO_LOCAL(ToLocal, String, String)
 MAKE_TO_LOCAL(ToLocal, Symbol, Symbol)
+MAKE_TO_LOCAL(ToLocal, Private, Private)
 MAKE_TO_LOCAL(ToLocal, JSRegExp, RegExp)
 MAKE_TO_LOCAL(ToLocal, JSObject, Object)
 MAKE_TO_LOCAL(ToLocal, JSArray, Array)