[strong] Strong classes can't extend null

src/compiler/ast-graph-builder.cc

Index: src/compiler/ast-graph-builder.cc
diff --git a/src/compiler/ast-graph-builder.cc b/src/compiler/ast-graph-builder.cc
index c8b0a2daac836b9eab02c05aa6b41b2e8b7a1336..fd1b6960d094b5b7ec47a20f1996d828737bf949 100644
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -1562,7 +1562,10 @@ void AstGraphBuilder::VisitClassLiteralContents(ClassLiteral* expr) {
   Node* script = jsgraph()->Constant(info()->script());
   Node* start = jsgraph()->Constant(expr->start_position());
   Node* end = jsgraph()->Constant(expr->end_position());
-  const Operator* opc = javascript()->CallRuntime(Runtime::kDefineClass, 6);
+  const Operator* opc = javascript()->CallRuntime(
+      is_strong(language_mode()) ? Runtime::kDefineClassStrong
+                                 : Runtime::kDefineClass,
+      6);
   Node* literal = NewNode(opc, name, extends, constructor, script, start, end);
   PrepareFrameState(literal, expr->CreateLiteralId(),
                     OutputFrameStateCombine::Push());