Serializer: clear next link in weak cells.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index df1ba3129f859c61163561df1e709de6d1b2dd4a..bad4528ff4dee805a10f0d4532960276a8c29eb1 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -3126,7 +3126,7 @@ AllocationResult Heap::AllocateWeakCell(HeapObject* value) {
   }
   result->set_map_no_write_barrier(weak_cell_map());
   WeakCell::cast(result)->initialize(value);
-  WeakCell::cast(result)->set_next(the_hole_value(), SKIP_WRITE_BARRIER);
+  WeakCell::cast(result)->clear_next(this);
   return result;
 }