[strong] Strong classes can't extend null

src/full-codegen.cc

 // Copyright 2012 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/v8.h"
 
 #include "src/ast.h"
 #include "src/ast-numbering.h"
 #include "src/code-factory.h"
 #include "src/codegen.h"
@@ skipping 1166 matching lines @@
     } else {
       __ Push(isolate()->factory()->the_hole_value());
     }
 
     VisitForStackValue(lit->constructor());
 
     __ Push(script());
     __ Push(Smi::FromInt(lit->start_position()));
     __ Push(Smi::FromInt(lit->end_position()));
 
-    __ CallRuntime(Runtime::kDefineClass, 6);
+    __ CallRuntime(is_strong(language_mode()) ? Runtime::kDefineClassStrong
+                                              : Runtime::kDefineClass,
+                   6);
     PrepareForBailoutForId(lit->CreateLiteralId(), TOS_REG);
 
     int store_slot_index = 0;
     EmitClassDefineProperties(lit, &store_slot_index);
 
     if (lit->scope() != NULL) {
       DCHECK_NOT_NULL(lit->class_variable_proxy());
       FeedbackVectorICSlot slot = FLAG_vector_stores
                                       ? lit->GetNthSlot(store_slot_index++)
                                       : FeedbackVectorICSlot::Invalid();
@@ skipping 270 matching lines @@
   codegen_->PrepareForBailoutForId(exit_id_, NO_REGISTERS);
   codegen_->scope_ = saved_scope_;
 }
 
 
 #undef __
 
 
 }  // namespace internal
 }  // namespace v8