[keys] support shadowing keys in the KeyAccumulator

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index b6931e0eef59dbaba496698a2915531654acd3e2..c52a17bef6192a1203d7d6acfc388ae03b538d34 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1002,6 +1002,7 @@ template <class C> inline bool Is(Object* obj);
   V(PropertyCell)                \
   V(WeakCell)                    \
   V(ObjectHashTable)             \
+  V(ObjectHashSet)               \
   V(WeakHashTable)               \
   V(OrderedHashTable)
 
@@ -3230,6 +3231,8 @@ class HashTable : public HashTableBase {
   inline int FindEntry(Key key);
   inline int FindEntry(Isolate* isolate, Key key, int32_t hash);
   int FindEntry(Isolate* isolate, Key key);
+  inline bool Has(Isolate* isolate, Key key);
+  inline bool Has(Key key);
 
   // Rehashes the table in-place.
   void Rehash(Key key);
@@ -3456,11 +3459,13 @@ class Dictionary: public HashTable<Derived, Shape, Key> {
 
   // Collect the keys into the given KeyAccumulator, in ascending chronological
   // order of property creation.
-  static void CollectKeysTo(Handle<Dictionary<Derived, Shape, Key> > dictionary,
-                            KeyAccumulator* keys, PropertyFilter filter);
+  static void CollectKeysTo(Handle<Dictionary<Derived, Shape, Key>> dictionary,
+                            KeyAccumulator* keys);
 
   // Copies enumerable keys to preallocated fixed array.
-  void CopyEnumKeysTo(FixedArray* storage);
+  static void CopyEnumKeysTo(Handle<Dictionary<Derived, Shape, Key>> dictionary,
+                             Handle<FixedArray> storage, KeyCollectionMode mode,
+                             KeyAccumulator* accumulator);
 
   // Accessors for next enumeration index.
   void SetNextEnumerationIndex(int index) {
@@ -3806,6 +3811,23 @@ class ObjectHashTable: public HashTable<ObjectHashTable,
   }
 };
 
+class ObjectHashSetShape : public ObjectHashTableShape {
+ public:
+  static const int kPrefixSize = 0;
+  static const int kEntrySize = 1;
+};
+
+class ObjectHashSet
+    : public HashTable<ObjectHashSet, ObjectHashSetShape, Handle<Object>> {
+ public:
+  static Handle<ObjectHashSet> Add(Handle<ObjectHashSet> set,
+                                   Handle<Object> key);
+
+  inline bool Has(Isolate* isolate, Handle<Object> key, int32_t hash);
+  inline bool Has(Isolate* isolate, Handle<Object> key);
+
+  DECLARE_CAST(ObjectHashSet)
+};
 
 // OrderedHashTable is a HashTable with Object keys that preserves
 // insertion order. There are Map and Set interfaces (OrderedHashMap