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

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index a90f9c9e46849c56ae8efcd1102c20c1e333d61a..06e62d6f10b2c1b0241b174d89e80410a4492c1d 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -779,6 +779,10 @@ void Isolate::ReportFailedAccessCheck(Handle<JSObject> receiver) {
 
 
 bool Isolate::IsInternallyUsedPropertyName(Handle<Object> name) {
+  if (name->IsSymbol()) {
+    return (Handle<Symbol>::cast(name)->is_private()) &&
+           Handle<Symbol>::cast(name)->is_own();
+  }
   return name.is_identical_to(factory()->hidden_string());
 }
 
@@ -2528,6 +2532,9 @@ Handle<JSObject> Isolate::GetSymbolRegistry() {
       Handle<JSObject> obj = factory()->NewJSObjectFromMap(map);
       JSObject::NormalizeProperties(obj, KEEP_INOBJECT_PROPERTIES, 8,
                                     "SetupSymbolRegistry");
+      if (strcmp(nested[i], "private_intern") == 0) {
+        heap()->AddPrivateGlobalSymbols(obj);
+      }
       JSObject::SetProperty(registry, name, obj, STRICT).Assert();
     }
   }