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

src/heap/heap.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/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/context-slot-cache.h"
 #include "src/base/bits.h"
@@ skipping 1577 matching lines @@
   RelocationLock relocation_lock(this);
   // There are soft limits in the allocation code, designed to trigger a mark
   // sweep collection by failing allocations. There is no sense in trying to
   // trigger one during scavenge: scavenges allocation should always succeed.
   AlwaysAllocateScope scope(isolate());
 
   // Bump-pointer allocations done during scavenge are not real allocations.
   // Pause the inline allocation steps.
   PauseAllocationObserversScope pause_observers(this);
 
+  mark_compact_collector()->sweeper().EnsureNewSpaceCompleted();
+
   gc_state_ = SCAVENGE;
 
   // Implements Cheney's copying algorithm
   LOG(isolate_, ResourceEvent("scavenge", "begin"));
 
   // Used for updating survived_since_last_expansion_ at function end.
   intptr_t survived_watermark = PromotedSpaceSizeOfObjects();
 
   scavenge_collector_->SelectScavengingVisitorsTable();
 
@@ skipping 4876 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8