Simplify the write barrier.

src/mark-compact.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1724 matching lines @@
 
     const MarkBit::CellType next_cell = cells[cell_index + 1];
     MarkBit::CellType grey_objects = current_cell &
         ((current_cell >> 1) | (next_cell << (Bitmap::kBitsPerCell - 1)));
 
     int offset = 0;
     while (grey_objects != 0) {
       int trailing_zeros = CompilerIntrinsics::CountTrailingZeros(grey_objects);
       grey_objects >>= trailing_zeros;
       offset += trailing_zeros;
-      MarkBit markbit(&cells[cell_index], 1 << offset, false);
+      MarkBit markbit(&cells[cell_index], 1 << offset);
       ASSERT(Marking::IsGrey(markbit));
       Marking::GreyToBlack(markbit);
       Address addr = cell_base + offset * kPointerSize;
       HeapObject* object = HeapObject::FromAddress(addr);
       MemoryChunk::IncrementLiveBytes(object->address(), object->Size());
       marking_deque->PushBlack(object);
       if (marking_deque->IsFull()) return;
       offset += 2;
       grey_objects >>= 2;
     }
@@ skipping 2018 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal