[Arguments] Introduce a new backing store for non-strict arguments objects.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index 958e524c205f80f84738b50ce8edfdc35ef8b658..40e14d24bd4822dd41f81093c6f7e76b425cf6d8 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -103,6 +103,7 @@ inline Heap* _inline_get_heap_();
   V(Map, external_int_array_map, ExternalIntArrayMap)                          \
   V(Map, external_unsigned_int_array_map, ExternalUnsignedIntArrayMap)         \
   V(Map, external_float_array_map, ExternalFloatArrayMap)                      \
+  V(Map, non_strict_arguments_elements_map, NonStrictArgumentsElementsMap)     \
   V(Map, context_map, ContextMap)                                              \
   V(Map, catch_context_map, CatchContextMap)                                   \
   V(Map, code_map, CodeMap)                                                    \