[heap] Iterate handles with special left-trim visitor

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 1badd964393b60b3cd41bd0b71247e6edcb109a4..3673dc1152983261fa2e0e17d2abf0d6e2ad8023 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -632,12 +632,6 @@ class Heap {
   // stored on the map to facilitate fast dispatch for {StaticVisitorBase}.
   static int GetStaticVisitorIdForMap(Map* map);
 
-  // We cannot avoid stale handles to left-trimmed objects, but can only make
-  // sure all handles still needed are updated. Filter out a stale pointer
-  // and clear the slot to allow post processing of handles (needed because
-  // the sweeper might actually free the underlying page).
-  inline bool PurgeLeftTrimmedObject(Object** object);
-
   // Notifies the heap that is ok to start marking or other activities that
   // should not happen during deserialization.
   void NotifyDeserializationComplete();