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

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 63d41c08a0214df9c93dcb66c63a82097c4ad9e7..ae095782c380c1c5cb0109dba436e9374260be82 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -540,6 +540,15 @@
   });
   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() {