Revert of Concurrently unmap free pages.

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 4c8db42035bb8c5722fe9b2fbe73b35d87f43f54..af6894c5755b2a6d7a14a853c3d3fd1ddb83de73 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -519,15 +519,12 @@
     SweepInParallel(heap()->paged_space(CODE_SPACE), 0);
     SweepInParallel(heap()->paged_space(MAP_SPACE), 0);
   }
-
+  // Wait twice for both jobs.
   if (heap()->concurrent_sweeping_enabled()) {
     pending_sweeper_jobs_semaphore_.Wait();
     pending_sweeper_jobs_semaphore_.Wait();
     pending_sweeper_jobs_semaphore_.Wait();
   }
-
-  heap()->WaitUntilUnmappingOfFreeChunksCompleted();
-
   ParallelSweepSpacesComplete();
   sweeping_in_progress_ = false;
   RefillFreeList(heap()->paged_space(OLD_SPACE));