Only use FreeSpace objects in the free list.

src/allocation-tracker.cc

Index: src/allocation-tracker.cc
diff --git a/src/allocation-tracker.cc b/src/allocation-tracker.cc
index 7534ffb82fd21f007befd70b52dd410dd455335d..1ad86b88ff8679a1dbf9568eaa8ee7fd022f331c 100644
--- a/src/allocation-tracker.cc
+++ b/src/allocation-tracker.cc
@@ -227,9 +227,7 @@ void AllocationTracker::AllocationEvent(Address addr, int size) {
 
   // Mark the new block as FreeSpace to make sure the heap is iterable
   // while we are capturing stack trace.
-  FreeListNode::FromAddress(addr)->set_size(heap, size);
-  DCHECK_EQ(HeapObject::FromAddress(addr)->Size(), size);
-  DCHECK(FreeListNode::IsFreeListNode(HeapObject::FromAddress(addr)));
+  heap->CreateFillerObjectAt(addr, size);
 
   Isolate* isolate = heap->isolate();
   int length = 0;