[heap] Properly handle --noconcurrent-sweeping flag in page unmapper.

src/heap/spaces.cc

Index: src/heap/spaces.cc
diff --git a/src/heap/spaces.cc b/src/heap/spaces.cc
index 8710a5f54b00057d0a093c210200aea2f7bac1a0..8982a2953273abbe35993b57ab63ee43d42ae0d7 100644
--- a/src/heap/spaces.cc
+++ b/src/heap/spaces.cc
@@ -398,7 +398,7 @@ bool MemoryAllocator::CanFreeMemoryChunk(MemoryChunk* chunk) {
   // We cannot free memory chunks in new space while the sweeper is running
   // since a sweeper thread might be stuck right before trying to lock the
   // corresponding page.
-  return !chunk->InNewSpace() || (mc == nullptr) ||
+  return !chunk->InNewSpace() || (mc == nullptr) || !FLAG_concurrent_sweeping ||
          mc->sweeper().IsSweepingCompleted();
 }