Revert of [heap] Don't unmap new space pages while sweeping is active

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 524 matching lines @@
   ForAllSweepingSpaces([this](AllocationSpace space) {
     if (space == NEW_SPACE) {
       swept_list_[NEW_SPACE].Clear();
     }
     DCHECK(sweeping_list_[space].empty());
   });
   late_pages_ = false;
   sweeping_in_progress_ = false;
 }
 
+void MarkCompactCollector::Sweeper::EnsureNewSpaceCompleted() {
+  if (!sweeping_in_progress_) return;
+  if (!FLAG_concurrent_sweeping || !IsSweepingCompleted()) {
+    for (Page* p : *heap_->new_space()) {
+      SweepOrWaitUntilSweepingCompleted(p);
+    }
+  }
+}
+
 void MarkCompactCollector::EnsureSweepingCompleted() {
   if (!sweeper().sweeping_in_progress()) return;
 
   sweeper().EnsureCompleted();
   heap()->old_space()->RefillFreeList();
   heap()->code_space()->RefillFreeList();
   heap()->map_space()->RefillFreeList();
 
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap && !evacuation()) {
@@ skipping 3473 matching lines @@
       // The target is always in old space, we don't have to record the slot in
       // the old-to-new remembered set.
       DCHECK(!heap()->InNewSpace(target));
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8