Change RecordSlot interface. Make it more robust by replacing anchor slot with actual object.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 750827968dcd757edff47ece2ed0948930aa688f..45ff17e4b2e366e6c45e6388d64a6d8058044d85 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -952,9 +952,9 @@ class Heap {
   void IterateWeakRoots(ObjectVisitor* v, VisitMode mode);
 
   // Iterate pointers to from semispace of new space found in memory interval
-  // from start to end.
-  void IterateAndMarkPointersToFromSpace(bool record_slots, Address start,
-                                         Address end,
+  // from start to end within |object|.
+  void IterateAndMarkPointersToFromSpace(HeapObject* object, Address start,
+                                         Address end, bool record_slots,
                                          ObjectSlotCallback callback);
 
   // Returns whether the object resides in new space.