new classes: implement new.target passing to superclass constructor.

src/runtime/runtime-classes.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 <stdlib.h>
 #include <limits>
 
 #include "src/v8.h"
 
 #include "src/isolate-inl.h"
@@ skipping 99 matching lines @@
   map->SetPrototype(prototype_parent);
   map->set_constructor(*constructor);
   Handle<JSObject> prototype = isolate->factory()->NewJSObjectFromMap(map);
 
   Handle<String> name_string = name->IsString()
                                    ? Handle<String>::cast(name)
                                    : isolate->factory()->empty_string();
   constructor->shared()->set_name(*name_string);
 
   if (FLAG_experimental_classes) {
-    if (!super_class->IsTheHole() && !super_class->IsNull()) {
+    if (!super_class->IsTheHole()) {
       Handle<Code> stub(isolate->builtins()->JSConstructStubForDerived());
       constructor->shared()->set_construct_stub(*stub);
     }
   }
 
   JSFunction::SetPrototype(constructor, prototype);
   PropertyAttributes attribs =
       static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE | READ_ONLY);
   RETURN_FAILURE_ON_EXCEPTION(
       isolate, JSObject::SetOwnPropertyIgnoreAttributes(
@@ skipping 323 matching lines @@
   }
 
   Handle<Object> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result,
       Execution::Call(isolate, proto_function, receiver, argc, argv, false));
   return *result;
 }
 }
 }  // namespace v8::internal