Use instance type in Object::IsErrorObject().

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 18599bfe51b4fe7bc917b2220181544307048244..2371efcbd5305f6c67ed152831d46593f7c5aa53 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -3008,19 +3008,7 @@ bool Value::IsNativeError() const {
   i::Handle<i::Object> obj = Utils::OpenHandle(this);
   if (!obj->IsJSObject()) return false;
   i::Handle<i::JSObject> js_obj = i::Handle<i::JSObject>::cast(obj);
-  i::Isolate* isolate = js_obj->GetIsolate();
-  i::Handle<i::Object> constructor(js_obj->map()->GetConstructor(), isolate);
-  if (!constructor->IsJSFunction()) return false;
-  i::Handle<i::JSFunction> function =
-      i::Handle<i::JSFunction>::cast(constructor);
-  if (!function->shared()->native()) return false;
-  return function.is_identical_to(isolate->error_function()) ||
-         function.is_identical_to(isolate->eval_error_function()) ||
-         function.is_identical_to(isolate->range_error_function()) ||
-         function.is_identical_to(isolate->reference_error_function()) ||
-         function.is_identical_to(isolate->syntax_error_function()) ||
-         function.is_identical_to(isolate->type_error_function()) ||
-         function.is_identical_to(isolate->uri_error_function());
+  return js_obj->map()->instance_type() == i::JS_ERROR_TYPE;

[jochen (gone - plz use gerrit), 2016/06/23 14:42:15]

why not just 

auto self = Utils::OpenHandle(this);
return i::Object::IsErrorObject(self);

 }