Fix processing of partially initialized JSWeakCollection.

src/objects-visiting-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_OBJECTS_VISITING_INL_H_
 #define V8_OBJECTS_VISITING_INL_H_
 
 
 namespace v8 {
 namespace internal {
@@ skipping 386 matching lines @@
 
 
 template<typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitWeakCollection(
     Map* map, HeapObject* object) {
   Heap* heap = map->GetHeap();
   JSWeakCollection* weak_collection =
       reinterpret_cast<JSWeakCollection*>(object);
   MarkCompactCollector* collector = heap->mark_compact_collector();
 
-  // Enqueue weak map in linked list of encountered weak maps.
+  // Enqueue weak collection in linked list of encountered weak collections.
   if (weak_collection->next() == heap->undefined_value()) {
     weak_collection->set_next(collector->encountered_weak_collections());
     collector->set_encountered_weak_collections(weak_collection);
   }
 
   // Skip visiting the backing hash table containing the mappings and the
   // pointer to the other enqueued weak collections, both are post-processed.
   StaticVisitor::VisitPointers(heap,
       HeapObject::RawField(object, JSWeakCollection::kPropertiesOffset),
       HeapObject::RawField(object, JSWeakCollection::kTableOffset));
   STATIC_ASSERT(JSWeakCollection::kTableOffset + kPointerSize ==
       JSWeakCollection::kNextOffset);
   STATIC_ASSERT(JSWeakCollection::kNextOffset + kPointerSize ==
       JSWeakCollection::kSize);
 
+  // Partially initialized weak collection is enqueued, but table is ignored.
   if (!weak_collection->table()->IsHashTable()) return;
 
   // Mark the backing hash table without pushing it on the marking stack.
   Object** slot = HeapObject::RawField(object, JSWeakCollection::kTableOffset);
   HeapObject* obj = HeapObject::cast(*slot);
   heap->mark_compact_collector()->RecordSlot(slot, slot, obj);
   StaticVisitor::MarkObjectWithoutPush(heap, obj);
 }
 
 
@@ skipping 526 matching lines @@
   RelocIterator it(this, mode_mask);
   for (; !it.done(); it.next()) {
     it.rinfo()->template Visit<StaticVisitor>(heap);
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_VISITING_INL_H_