Record the addresses of pages that are unmapped to aid

src/spaces.cc

Index: src/spaces.cc
===================================================================
--- src/spaces.cc	(revision 11059)
+++ src/spaces.cc	(working copy)
@@ -594,6 +594,9 @@
     PerformAllocationCallback(space, kAllocationActionFree, chunk->size());
   }
 
+  isolate_->heap()->RememberUnmappedPage(
+      reinterpret_cast<Address>(chunk), chunk->IsEvacuationCandidate());
+
   delete chunk->slots_buffer();
   delete chunk->skip_list();