Viewport <#document> at (0,0) content-size 800x600 children: not-inline
  BlockContainer <html> at (0,0) content-size 800x136 [BFC] children: not-inline
    BlockContainer <body> at (8,8) content-size 784x120 children: not-inline
      Box <div.flexContainer> at (8,8) content-size 784x120 flex-container(column) [FFC] children: not-inline
        BlockContainer <div.item> at (8,8) content-size 784x120 flex-item [BFC] children: not-inline
          BlockContainer <div.green> at (8,8) content-size 120x120 children: not-inline

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 800x136]
    PaintableWithLines (BlockContainer<BODY>) [8,8 784x120]
      PaintableBox (Box<DIV>.flexContainer) [8,8 784x120]
        PaintableWithLines (BlockContainer<DIV>.item) [8,8 784x120]
          PaintableWithLines (BlockContainer<DIV>.green) [8,8 120x120]
