Use instance type in Object.prototype.toString().

test/cctest/test-inobject-slack-tracking.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdlib.h>
 #include <sstream>
 #include <utility>
 
 #include "src/api.h"
 #include "src/objects.h"
@@ skipping 907 matching lines @@
 
 
 TEST(SubclassErrorBuiltin) {
   // Avoid eventual completion of in-object slack tracking.
   FLAG_inline_construct = false;
   FLAG_always_opt = false;
   CcTest::InitializeVM();
   v8::HandleScope scope(CcTest::isolate());
 
   const int first_field = 2;
-  TestSubclassBuiltin("A1", JS_OBJECT_TYPE, "Error", "'err'", first_field);
-  TestSubclassBuiltin("A2", JS_OBJECT_TYPE, "EvalError", "'err'", first_field);
-  TestSubclassBuiltin("A3", JS_OBJECT_TYPE, "RangeError", "'err'", first_field);
-  TestSubclassBuiltin("A4", JS_OBJECT_TYPE, "ReferenceError", "'err'",
+  TestSubclassBuiltin("A1", JS_ERROR_TYPE, "Error", "'err'", first_field);
+  TestSubclassBuiltin("A2", JS_ERROR_TYPE, "EvalError", "'err'", first_field);
+  TestSubclassBuiltin("A3", JS_ERROR_TYPE, "RangeError", "'err'", first_field);
+  TestSubclassBuiltin("A4", JS_ERROR_TYPE, "ReferenceError", "'err'",
                       first_field);
-  TestSubclassBuiltin("A5", JS_OBJECT_TYPE, "SyntaxError", "'err'",
-                      first_field);
-  TestSubclassBuiltin("A6", JS_OBJECT_TYPE, "TypeError", "'err'", first_field);
-  TestSubclassBuiltin("A7", JS_OBJECT_TYPE, "URIError", "'err'", first_field);
+  TestSubclassBuiltin("A5", JS_ERROR_TYPE, "SyntaxError", "'err'", first_field);
+  TestSubclassBuiltin("A6", JS_ERROR_TYPE, "TypeError", "'err'", first_field);
+  TestSubclassBuiltin("A7", JS_ERROR_TYPE, "URIError", "'err'", first_field);
 }
 
 
 TEST(SubclassErrorBuiltinNoInlineNew) {
   FLAG_inline_new = false;
   TestSubclassErrorBuiltin();
 }
 
 
 TEST(SubclassNumberBuiltin) {
@@ skipping 157 matching lines @@
   TestSubclassBuiltin("A1", JS_PROMISE_TYPE, "Promise",
                       "function(resolve, reject) { resolve('ok'); }",
                       first_field);
 }
 
 
 TEST(SubclassPromiseBuiltinNoInlineNew) {
   FLAG_inline_new = false;
   TestSubclassPromiseBuiltin();
 }