Revert "[heap] Make SlotSet allocation thread-safe and refactor code."

src/heap/spaces-inl.h

 // Copyright 2011 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.
 
 #ifndef V8_HEAP_SPACES_INL_H_
 #define V8_HEAP_SPACES_INL_H_
 
 #include "src/heap/incremental-marking.h"
 #include "src/heap/spaces.h"
 #include "src/isolate.h"
@@ skipping 312 matching lines @@
 
 void Page::MarkNeverAllocateForTesting() {
   DCHECK(this->owner()->identity() != NEW_SPACE);
   DCHECK(!IsFlagSet(NEVER_ALLOCATE_ON_PAGE));
   SetFlag(NEVER_ALLOCATE_ON_PAGE);
   reinterpret_cast<PagedSpace*>(owner())->free_list()->EvictFreeListItems(this);
 }
 
 void Page::MarkEvacuationCandidate() {
   DCHECK(!IsFlagSet(NEVER_EVACUATE));
-  DCHECK_NULL(slot_set<OLD_TO_OLD>());
-  DCHECK_NULL(typed_slot_set<OLD_TO_OLD>());
+  DCHECK_NULL(old_to_old_slots_);
+  DCHECK_NULL(typed_old_to_old_slots_);
   SetFlag(EVACUATION_CANDIDATE);
   reinterpret_cast<PagedSpace*>(owner())->free_list()->EvictFreeListItems(this);
 }
 
 void Page::ClearEvacuationCandidate() {
   if (!IsFlagSet(COMPACTION_WAS_ABORTED)) {
-    DCHECK_NULL(slot_set<OLD_TO_OLD>());
-    DCHECK_NULL(typed_slot_set<OLD_TO_OLD>());
+    DCHECK_NULL(old_to_old_slots_);
+    DCHECK_NULL(typed_old_to_old_slots_);
   }
   ClearFlag(EVACUATION_CANDIDATE);
   InitializeFreeListCategories();
 }
 
 MemoryChunkIterator::MemoryChunkIterator(Heap* heap)
     : heap_(heap),
       state_(kOldSpaceState),
       old_iterator_(heap->old_space()->begin()),
       code_iterator_(heap->code_space()->begin()),
@@ skipping 316 matching lines @@
     other->allocation_info_.Reset(nullptr, nullptr);
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_INL_H_