[es6] Introduce spec compliant IsConstructor.

src/runtime/runtime-object.cc

 // Copyright 2014 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 "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/debug/debug.h"
 #include "src/isolate-inl.h"
@@ skipping 1038 matching lines @@
         isolate, NewTypeError(MessageTemplate::kNotConstructor, constructor));
   }
 
   Handle<JSFunction> function = Handle<JSFunction>::cast(constructor);
 
   CHECK(original_constructor->IsJSFunction());
   Handle<JSFunction> original_function =
       Handle<JSFunction>::cast(original_constructor);
 
 
-  // If function should not have prototype, construction is not allowed. In this
-  // case generated code bailouts here, since function has no initial_map.
-  if (!function->should_have_prototype() && !function->shared()->bound()) {
+  // Check that function is a constructor.
+  if (!function->IsConstructor()) {
     THROW_NEW_ERROR_RETURN_FAILURE(
         isolate, NewTypeError(MessageTemplate::kNotConstructor, constructor));
   }
 
   Debug* debug = isolate->debug();
   // Handle stepping into constructors if step into is active.
   if (debug->StepInActive()) debug->HandleStepIn(function, true);
 
   if (function->has_initial_map()) {
     if (function->initial_map()->instance_type() == JS_FUNCTION_TYPE) {
@@ skipping 538 matching lines @@
 RUNTIME_FUNCTION(Runtime_IsAccessCheckNeeded) {
   SealHandleScope shs(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_CHECKED(Object, object, 0);
   return isolate->heap()->ToBoolean(object->IsAccessCheckNeeded());
 }
 
 
 }  // namespace internal
 }  // namespace v8