Add kHeaderSize constant to SeqString.

src/spaces.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 420 matching lines @@
   chunk->set_owner(owner);
   chunk->InitializeReservedMemory();
   chunk->slots_buffer_ = NULL;
   chunk->skip_list_ = NULL;
   chunk->ResetLiveBytes();
   Bitmap::Clear(chunk);
   chunk->initialize_scan_on_scavenge(false);
   chunk->SetFlag(WAS_SWEPT_PRECISELY);
 
   ASSERT(OFFSET_OF(MemoryChunk, flags_) == kFlagsOffset);
+  ASSERT(OFFSET_OF(MemoryChunk, live_byte_count_) == kLiveBytesOffset);
 
   if (executable == EXECUTABLE) chunk->SetFlag(IS_EXECUTABLE);
 
   if (owner == heap->old_data_space()) chunk->SetFlag(CONTAINS_ONLY_DATA);
 
   return chunk;
 }
 
 
 void MemoryChunk::InsertAfter(MemoryChunk* other) {
@@ skipping 365 matching lines @@
       // All the interior pointers should be contained in the heap.
       int size = object->Size();
       object->IterateBody(map->instance_type(), size, visitor);
       if (Marking::IsBlack(Marking::MarkBitFrom(object))) {
         black_size += size;
       }
 
       ASSERT(object->address() + size <= top);
       end_of_previous_object = object->address() + size;
     }
-
     CHECK_LE(black_size, page->LiveBytes());
   }
   ASSERT(allocation_pointer_found_in_space);
 }
 #endif
 
 
 // -----------------------------------------------------------------------------
 // NewSpace implementation
 
@@ skipping 1683 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal