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

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 9de8006946ebc6e3908fd5341974f7ba5a26abe1..6e0d24ccaa3251451cddea41221b7c8516cac652 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -1411,10 +1411,8 @@ class RootMarkingVisitor : public ObjectVisitor {
   void MarkObjectByPointer(Object** p) {
     if (!(*p)->IsHeapObject()) return;
 
+    // Replace flat cons strings in place.
     HeapObject* object = HeapObject::cast(*p);
-
-    if (collector_->heap()->PurgeLeftTrimmedObject(p)) return;
-
     MarkBit mark_bit = Marking::MarkBitFrom(object);
     if (Marking::IsBlackOrGrey(mark_bit)) return;