Class methods should be non enumerable

src/runtime/runtime-classes.cc

Index: src/runtime/runtime-classes.cc
diff --git a/src/runtime/runtime-classes.cc b/src/runtime/runtime-classes.cc
index 00567d432330e0e329e1ffd6b15b0c690f7c103d..7e512d4fbf3f31c4a1843dc17b619e91650d0f37 100644
--- a/src/runtime/runtime-classes.cc
+++ b/src/runtime/runtime-classes.cc
@@ -159,11 +159,12 @@ RUNTIME_FUNCTION(Runtime_DefineClassMethod) {
   uint32_t index;
   if (name->AsArrayIndex(&index)) {
     RETURN_FAILURE_ON_EXCEPTION(
-        isolate, JSObject::SetOwnElement(object, index, function, STRICT));
+        isolate,
+        JSObject::SetOwnElement(object, index, function, DONT_ENUM, STRICT));
   } else {
     RETURN_FAILURE_ON_EXCEPTION(
-        isolate,
-        JSObject::SetOwnPropertyIgnoreAttributes(object, name, function, NONE));
+        isolate, JSObject::SetOwnPropertyIgnoreAttributes(object, name,
+                                                          function, DONT_ENUM));
   }
   return isolate->heap()->undefined_value();
 }