Revert of [heap] Uncommit pooled pages concurrently

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 66feadc6b84368b7ef13bea9f5ebd36283f1de86..f93329402142e0af400d642561b5f2dc24ac724b 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -778,6 +778,11 @@
 
   inline bool OldGenerationAllocationLimitReached();
 
+  void QueueMemoryChunkForFree(MemoryChunk* chunk);
+  void FreeQueuedChunks(MemoryChunk* list_head);
+  void FreeQueuedChunks();
+  void WaitUntilUnmappingOfFreeChunksCompleted();
+
   // Completely clear the Instanceof cache (to stop it keeping objects alive
   // around a GC).
   inline void CompletelyClearInstanceofCache();
@@ -1385,6 +1390,7 @@
 
  private:
   class PretenuringScope;
+  class UnmapFreeMemoryTask;
 
   // External strings table is a place where all external strings are
   // registered.  We need to keep track of such strings to properly
@@ -2201,6 +2207,12 @@
   GCCallbackFlags current_gc_callback_flags_;
 
   ExternalStringTable external_string_table_;
+
+  MemoryChunk* chunks_queued_for_free_;
+
+  size_t concurrent_unmapping_tasks_active_;
+
+  base::Semaphore pending_unmapping_tasks_semaphore_;
 
   base::Mutex relocation_mutex_;