[heap] Filter out stale left-trimmed handles for scavenges

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index eb5fc790900da0df9bf82541d656df6da55808a2..adee093424cd9063ca4bcb712d110a2d91173ae8 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1491,7 +1491,7 @@ class MapWord BASE_EMBEDDED {
   // True if this map word is a forwarding address for a scavenge
   // collection.  Only valid during a scavenge collection (specifically,
   // when all map words are heap object pointers, i.e. not during a full GC).
-  inline bool IsForwardingAddress() const;
+  inline bool IsForwardingAddress();
 
   // Create a map word from a forwarding address.
   static inline MapWord FromForwardingAddress(HeapObject* object);