Prototype of mark-and-compact support for Harmony weak maps.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 58b6f281b4b986ebd7ea6f7946830b0d90eadd42..9cbb8596aee6b40fbc61522ab01b7a852fc73d4e 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2974,6 +2974,11 @@ class ObjectHashTable: public HashTable<ObjectHashTableShape, JSObject*> {
     return reinterpret_cast<ObjectHashTable*>(obj);
   }
 
+  // Returns the value at entry.
+  Object* ValueAt(int entry) {
+    return this->get(EntryToIndex(entry) + 1);
+  }
+
   // Looks up the value associated with the given key. The undefined value is
   // returned in case the key is not present.
   Object* Lookup(JSObject* key);
@@ -2983,8 +2988,11 @@ class ObjectHashTable: public HashTable<ObjectHashTableShape, JSObject*> {
   MUST_USE_RESULT MaybeObject* Put(JSObject* key, Object* value);
 
  private:
+  friend class MarkCompactCollector;
+
   void AddEntry(int entry, JSObject* key, Object* value);
-  void RemoveEntry(int entry);
+  void RemoveEntry(int entry, Heap* heap);
+  inline void RemoveEntry(int entry);
 };
 
 
@@ -6628,6 +6636,12 @@ class JSWeakMap: public JSObject {
   // [table]: the backing hash table mapping keys to values.
   DECL_ACCESSORS(table, ObjectHashTable)
 
+  // [next]: linked list of encountered weak maps during GC.
+  DECL_ACCESSORS(next, Object)
+
+  // Unchecked accessors to be used during GC.
+  inline ObjectHashTable* unchecked_table();
+
   // Casting.
   static inline JSWeakMap* cast(Object* obj);
 
@@ -6642,7 +6656,8 @@ class JSWeakMap: public JSObject {
 #endif
 
   static const int kTableOffset = JSObject::kHeaderSize;
-  static const int kSize = kTableOffset + kPointerSize;
+  static const int kNextOffset = kTableOffset + kPointerSize;
+  static const int kSize = kNextOffset + kPointerSize;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSWeakMap);