Use a private own symbol instead of a hidden property for hash codes

src/runtime/runtime-symbol.cc

Index: src/runtime/runtime-symbol.cc
diff --git a/src/runtime/runtime-symbol.cc b/src/runtime/runtime-symbol.cc
index 31b6bed22ef390922502d66148edd77ccaf45899..f38c97548a06cc96368212628a5866dee2b03703 100644
--- a/src/runtime/runtime-symbol.cc
+++ b/src/runtime/runtime-symbol.cc
@@ -37,8 +37,7 @@ RUNTIME_FUNCTION(Runtime_CreatePrivateOwnSymbol) {
   DCHECK(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(Object, name, 0);
   RUNTIME_ASSERT(name->IsString() || name->IsUndefined());
-  Handle<Symbol> symbol = isolate->factory()->NewPrivateOwnSymbol();
-  if (name->IsString()) symbol->set_name(*name);
+  Handle<Symbol> symbol = isolate->factory()->NewPrivateOwnSymbol(name);
   return *symbol;
 }
 
@@ -57,9 +56,7 @@ RUNTIME_FUNCTION(Runtime_CreateGlobalPrivateOwnSymbol) {
       isolate, symbol, Object::GetPropertyOrElement(privates, name));
   if (!symbol->IsSymbol()) {
     DCHECK(symbol->IsUndefined());
-    symbol = isolate->factory()->NewPrivateSymbol();
-    Handle<Symbol>::cast(symbol)->set_name(*name);
-    Handle<Symbol>::cast(symbol)->set_is_own(true);
+    symbol = isolate->factory()->NewPrivateOwnSymbol(name);
     JSObject::SetProperty(Handle<JSObject>::cast(privates), name, symbol,
                           STRICT).Assert();
   }