Ensure that privates are private.

extensions/renderer/module_system_unittest.cc

Index: extensions/renderer/module_system_unittest.cc
diff --git a/extensions/renderer/module_system_unittest.cc b/extensions/renderer/module_system_unittest.cc
index 38756fd3857ccaa8aa13172d0f803496bd76e1b9..b91715b1a336431db517ee8120b5e6adf500ea6f 100644
--- a/extensions/renderer/module_system_unittest.cc
+++ b/extensions/renderer/module_system_unittest.cc
@@ -505,4 +505,14 @@ TEST_F(ModuleSystemTest, TestRequireAsyncFromContextWithNoModuleSystem) {
   RunResolvedPromises();
 }
 
+TEST_F(ModuleSystemTest, TestPrivatesIsPrivate) {
+  ModuleSystem::NativesEnabledScope natives_enabled_scope(
+      env()->module_system());
+  env()->RegisterModule(
+      "test",
+      "var v = privates({});"
+      "requireNative('assert').AssertFalse(v instanceof Object);");
+  env()->module_system()->Require("test");
+}
+
 }  // namespace extensions