[strong] Implement revised strong class semantics

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 "src/runtime/runtime-utils.h"
 
 #include <stdlib.h>
 #include <limits>
 
 #include "src/arguments.h"
@@ skipping 124 matching lines @@
 
   Handle<Map> map =
       isolate->factory()->NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
   if (constructor->map()->is_strong()) {
     map->set_is_strong();
     if (super_class->IsNull()) {
       // Strong class is not permitted to extend null.
       THROW_NEW_ERROR(isolate, NewTypeError(MessageTemplate::kStrongExtendNull),
                       Object);
     }
-  } else {
-    if (Handle<HeapObject>::cast(super_class)->map()->is_strong()) {
-      // Weak class is not permitted to extend strong class.
-      THROW_NEW_ERROR(isolate,
-                      NewTypeError(MessageTemplate::kStrongWeakExtend, name),
-                      Object);
-    }
   }
   Map::SetPrototype(map, prototype_parent);
   map->SetConstructor(*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);
 
@@ skipping 378 matching lines @@
   Handle<Object> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result,
       Execution::Call(isolate, reflect, isolate->factory()->undefined_value(),
                       arraysize(argv), argv));
 
   return *result;
 }
 }  // namespace internal
 }  // namespace v8