Move hash code from hidden string to a private symbol

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index 8eaa216ee84646ba9f3d0d42c8c6d2188be5d69f..3b675f200b609160a288cf33fb3173cce381f6d0 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -233,7 +233,7 @@ class Factory final {
   // Create a symbol.
   Handle<Symbol> NewSymbol();
   Handle<Symbol> NewPrivateSymbol();
-  Handle<Symbol> NewPrivateOwnSymbol();
+  Handle<Symbol> NewPrivateOwnSymbol(Handle<Object> name);
 
   // Create a global (but otherwise uninitialized) context.
   Handle<Context> NewNativeContext();