Replace PushIfAbsent by a Stack object

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 26b927d2e4b68d3f1662806e000e04306737682d..164f59bf53193dfd2123b4c93ada6a718018d1eb 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -3485,10 +3485,6 @@ class Dictionary: public HashTable<Derived, Shape, Key> {
     return NumberOfElementsFilterAttributes(ENUMERABLE_STRINGS);
   }
 
-  // Returns true if the dictionary contains any elements that are non-writable,
-  // non-configurable, non-enumerable, or have getters/setters.
-  bool HasComplexElements();
-
   enum SortMode { UNSORTED, SORTED };
 
   // Fill in details for properties into storage.
@@ -3721,6 +3717,10 @@ class SeededNumberDictionary
 
   void UpdateMaxNumberKey(uint32_t key, bool used_as_prototype);
 
+  // Returns true if the dictionary contains any elements that are non-writable,
+  // non-configurable, non-enumerable, or have getters/setters.
+  bool HasComplexElements();
+
   // If slow elements are required we will never go back to fast-case
   // for the elements kept in this dictionary.  We require slow
   // elements if an element has been added at an index larger than