[heap] Remove markbits getter from raw address

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 8b800ae93b31b4dfeafdb8fcf4c68b231b1d767c..1f142d52375ecb2b2984e08629320e4a9fb74b55 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -747,7 +747,8 @@ class Heap {
   // when introducing gaps within pages. If slots could have been recorded in
   // the freed area, then pass ClearRecordedSlots::kYes as the mode. Otherwise,
   // pass ClearRecordedSlots::kNo.
-  void CreateFillerObjectAt(Address addr, int size, ClearRecordedSlots mode);
+  HeapObject* CreateFillerObjectAt(Address addr, int size,
+                                   ClearRecordedSlots mode);
 
   bool CanMoveObjectStart(HeapObject* object);