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

src/spaces-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 314 matching lines @@
   ASSERT(length <= string->length());
   ASSERT(string->IsSeqString());
   ASSERT(string->address() + StringType::SizeFor(string->length()) ==
          allocation_info_.top);
   Address old_top = allocation_info_.top;
   allocation_info_.top =
       string->address() + StringType::SizeFor(length);
   string->set_length(length);
   if (Marking::IsBlack(Marking::MarkBitFrom(string))) {
     int delta = static_cast<int>(old_top - allocation_info_.top);
-    MemoryChunk::IncrementLiveBytes(string->address(), -delta);
+    MemoryChunk::IncrementLiveBytesFromMutator(string->address(), -delta);
   }
 }
 
 
 bool FreeListNode::IsFreeListNode(HeapObject* object) {
   Map* map = object->map();
   Heap* heap = object->GetHeap();
   return map == heap->raw_unchecked_free_space_map()
       || map == heap->raw_unchecked_one_pointer_filler_map()
       || map == heap->raw_unchecked_two_pointer_filler_map();
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_INL_H_