Viewport <#document> at (0,0) content-size 800x600 children: not-inline
  BlockContainer <html> at (0,0) content-size 800x106 [BFC] children: not-inline
    BlockContainer <body> at (8,8) content-size 784x90 children: not-inline
      BlockContainer <div.upper> at (8,8) content-size 784x20 children: not-inline
      BlockContainer <div.bfc> at (8,78) content-size 784x20 [BFC] children: not-inline
        BlockContainer <div.inner> at (8,78) content-size 20x20 children: not-inline
