[es6] Reintroduce the instanceof operator in the backends.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index ef00aa07f0232732b4445522235de4854fc2d59a..cbc6d72ad839a31822e64cbd93df6503ccca5133 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -2839,6 +2839,10 @@ void Heap::CreateInitialObjects() {
   cell->set_value(the_hole_value());
   set_empty_property_cell(*cell);
 
+  cell = factory->NewPropertyCell();
+  cell->set_value(Smi::FromInt(Isolate::kArrayProtectorValid));
+  set_has_instance_protector(*cell);
+
   Handle<Cell> is_concat_spreadable_cell = factory->NewCell(
       handle(Smi::FromInt(Isolate::kArrayProtectorValid), isolate()));
   set_is_concat_spreadable_protector(*is_concat_spreadable_cell);