Eagerly mark class prototypes as prototype.

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 105 matching lines @@
     } else {
       THROW_NEW_ERROR(
           isolate,
           NewTypeError(MessageTemplate::kExtendsValueNotFunction, super_class),
           Object);
     }
   }
 
   Handle<Map> map =
       isolate->factory()->NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
+  map->set_is_prototype_map(true);
   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);
     }
   }
   Map::SetPrototype(map, prototype_parent);
   map->SetConstructor(*constructor);
@@ skipping 80 matching lines @@
   return isolate->heap()->undefined_value();
 }
 
 
 RUNTIME_FUNCTION(Runtime_FinalizeClassDefinition) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, constructor, 0);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, prototype, 1);
 
-  JSObject::MigrateSlowToFast(prototype, 0, "RuntimeToFastProperties");
   JSObject::MigrateSlowToFast(constructor, 0, "RuntimeToFastProperties");
 
   if (constructor->map()->is_strong()) {
     DCHECK(prototype->map()->is_strong());
     RETURN_FAILURE_ON_EXCEPTION(isolate, JSObject::Freeze(prototype));
     Handle<Object> result;
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result,
                                        JSObject::Freeze(constructor));
     return *result;
   }
@@ skipping 276 matching lines @@
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result,
       Execution::New(isolate, super_constructor, original_constructor,
                      argument_count, arguments.get()));
 
   return *result;
 }
 
 }  // namespace internal
 }  // namespace v8