MarkBit cleanup: They have to be accessed through Marking accessors.

src/heap/mark-compact-inl.h

 // 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.
 
 #ifndef V8_HEAP_MARK_COMPACT_INL_H_
 #define V8_HEAP_MARK_COMPACT_INL_H_
 
 #include "src/heap/mark-compact.h"
 #include "src/isolate.h"
 
@@ skipping 10 matching lines @@
 
 void MarkCompactCollector::SetFlags(int flags) {
   reduce_memory_footprint_ = ((flags & Heap::kReduceMemoryFootprintMask) != 0);
   abort_incremental_marking_ =
       ((flags & Heap::kAbortIncrementalMarkingMask) != 0);
 }
 
 
 void MarkCompactCollector::MarkObject(HeapObject* obj, MarkBit mark_bit) {
   DCHECK(Marking::MarkBitFrom(obj) == mark_bit);
-  if (!mark_bit.Get()) {
-    mark_bit.Set();
+  if (Marking::IsWhite(mark_bit)) {
+    Marking::WhiteToBlack(mark_bit);
     MemoryChunk::IncrementLiveBytesFromGC(obj->address(), obj->Size());
-    DCHECK(IsMarked(obj));
     DCHECK(obj->GetIsolate()->heap()->Contains(obj));
     marking_deque_.PushBlack(obj);
   }
 }
 
 
 void MarkCompactCollector::SetMark(HeapObject* obj, MarkBit mark_bit) {
-  DCHECK(!mark_bit.Get());
+  DCHECK(Marking::IsWhite(mark_bit));
   DCHECK(Marking::MarkBitFrom(obj) == mark_bit);
-  mark_bit.Set();
+  Marking::WhiteToBlack(mark_bit);
   MemoryChunk::IncrementLiveBytesFromGC(obj->address(), obj->Size());
 }
 
 
 bool MarkCompactCollector::IsMarked(Object* obj) {
   DCHECK(obj->IsHeapObject());
   HeapObject* heap_object = HeapObject::cast(obj);
-  return Marking::MarkBitFrom(heap_object).Get();
+  return Marking::IsBlackOrGrey(Marking::MarkBitFrom(heap_object));
 }
 
 
 void MarkCompactCollector::RecordSlot(Object** anchor_slot, Object** slot,
                                       Object* object,
                                       SlotsBuffer::AdditionMode mode) {
   Page* object_page = Page::FromAddress(reinterpret_cast<Address>(object));
   if (object_page->IsEvacuationCandidate() &&
       !ShouldSkipEvacuationSlotRecording(anchor_slot)) {
     if (!SlotsBuffer::AddTo(&slots_buffer_allocator_,
                             object_page->slots_buffer_address(), slot, mode)) {
       EvictEvacuationCandidate(object_page);
     }
   }
 }
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_MARK_COMPACT_INL_H_