Classes: Add basic support for properties

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index f53fb6c177c675e4e74c685f9633d011398220f6..f309eae9d1406150cd4dba059e238e0254d7c4ae 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -2744,9 +2744,11 @@ void MarkCompactCollector::ProcessAndClearWeakCells() {
   Object* weak_cell_obj = heap()->encountered_weak_cells();
   while (weak_cell_obj != Smi::FromInt(0)) {
     WeakCell* weak_cell = reinterpret_cast<WeakCell*>(weak_cell_obj);
-    HeapObject* value = weak_cell->value();
+    // We do not insert cleared weak cells into the list, so the value
+    // cannot be a Smi here.
+    HeapObject* value = HeapObject::cast(weak_cell->value());
     if (!MarkCompactCollector::IsMarked(value)) {
-      weak_cell->clear(undefined);
+      weak_cell->clear();
     } else {
       Object** slot = HeapObject::RawField(weak_cell, WeakCell::kValueOffset);
       heap()->mark_compact_collector()->RecordSlot(slot, slot, value);
@@ -2924,7 +2926,8 @@ class PointersUpdatingVisitor : public ObjectVisitor {
   }
 
   static inline void UpdateSlot(Heap* heap, Object** slot) {
-    Object* obj = *slot;
+    Object* obj = reinterpret_cast<Object*>(
+        base::NoBarrier_Load(reinterpret_cast<base::AtomicWord*>(slot)));
 
     if (!obj->IsHeapObject()) return;
 
@@ -2935,7 +2938,10 @@ class PointersUpdatingVisitor : public ObjectVisitor {
       DCHECK(heap->InFromSpace(heap_obj) ||
              MarkCompactCollector::IsOnEvacuationCandidate(heap_obj));
       HeapObject* target = map_word.ToForwardingAddress();
-      *slot = target;
+      base::NoBarrier_CompareAndSwap(
+          reinterpret_cast<base::AtomicWord*>(slot),
+          reinterpret_cast<base::AtomicWord>(obj),
+          reinterpret_cast<base::AtomicWord>(target));
       DCHECK(!heap->InFromSpace(target) &&
              !MarkCompactCollector::IsOnEvacuationCandidate(target));
     }