Revert of Concurrently unmap free pages.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index ad1a6e8cbed53e688c25de7647401809d6f5728a..0d7b77d0765723218213ceeecca9b9953574f8cc 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -1442,9 +1442,7 @@
 
   void QueueMemoryChunkForFree(MemoryChunk* chunk);
   void FilterStoreBufferEntriesOnAboutToBeFreedPages();
-  void FreeQueuedChunks(MemoryChunk* list_head);
   void FreeQueuedChunks();
-  void WaitUntilUnmappingOfFreeChunksCompleted();
 
   int gc_count() const { return gc_count_; }
 
@@ -1621,8 +1619,6 @@
   bool ShouldOptimizeForMemoryUsage() { return optimize_for_memory_usage_; }
 
  private:
-  class UnmapFreeMemoryTask;
-
   static const int kInitialStringTableSize = 2048;
   static const int kInitialEvalCacheSize = 64;
   static const int kInitialNumberStringCacheSize = 256;
@@ -2299,8 +2295,6 @@
   VisitorDispatchTable<ScavengingCallback> scavenging_visitors_table_;
 
   MemoryChunk* chunks_queued_for_free_;
-
-  base::Semaphore pending_unmap_job_semaphore_;
 
   base::Mutex relocation_mutex_;