When adjusting page's live bytes counter from the mutator adjust owners unswept free bytes counter.

src/incremental-marking-inl.h

 // 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 77 matching lines @@
 }
 
 
 void IncrementalMarking::BlackToGreyAndUnshift(HeapObject* obj,
                                                MarkBit mark_bit) {
   ASSERT(Marking::MarkBitFrom(obj) == mark_bit);
   ASSERT(obj->Size() >= 2*kPointerSize);
   ASSERT(IsMarking());
   Marking::BlackToGrey(mark_bit);
   int obj_size = obj->Size();
-  MemoryChunk::IncrementLiveBytes(obj->address(), -obj_size);
+  MemoryChunk::IncrementLiveBytesFromGC(obj->address(), -obj_size);
   bytes_scanned_ -= obj_size;
   int64_t old_bytes_rescanned = bytes_rescanned_;
   bytes_rescanned_ = old_bytes_rescanned + obj_size;
   if ((bytes_rescanned_ >> 20) != (old_bytes_rescanned >> 20)) {
     if (bytes_rescanned_ > 2 * heap_->PromotedSpaceSize()) {
       // If we have queued twice the heap size for rescanning then we are
       // going around in circles, scanning the same objects again and again
       // as the program mutates the heap faster than we can incrementally
       // trace it.  In this case we switch to non-incremental marking in
       // order to finish off this marking phase.
@@ skipping 15 matching lines @@
 
 
 void IncrementalMarking::WhiteToGrey(HeapObject* obj, MarkBit mark_bit) {
   Marking::WhiteToGrey(mark_bit);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_INCREMENTAL_MARKING_INL_H_