Serializer: support all alignment kinds.

src/heap/objects-visiting-inl.h

Index: src/heap/objects-visiting-inl.h
diff --git a/src/heap/objects-visiting-inl.h b/src/heap/objects-visiting-inl.h
index 9cd08c0bff23a672c97ce94b03f47d5d3af25c1e..433fc6deab3e0efc7cb921501d7757d1c42a2688 100644
--- a/src/heap/objects-visiting-inl.h
+++ b/src/heap/objects-visiting-inl.h
@@ -329,11 +329,11 @@ void StaticMarkingVisitor<StaticVisitor>::VisitWeakCell(Map* map,
                                                         HeapObject* object) {
   Heap* heap = map->GetHeap();
   WeakCell* weak_cell = reinterpret_cast<WeakCell*>(object);
-  Object* undefined = heap->undefined_value();
+  Object* the_hole = heap->the_hole_value();
   // Enqueue weak cell in linked list of encountered weak collections.
   // We can ignore weak cells with cleared values because they will always
   // contain smi zero.
-  if (weak_cell->next() == undefined && !weak_cell->cleared()) {
+  if (weak_cell->next() == the_hole && !weak_cell->cleared()) {
     weak_cell->set_next(heap->encountered_weak_cells(),
                         UPDATE_WEAK_WRITE_BARRIER);
     heap->set_encountered_weak_cells(weak_cell);