Viewport <#document> at [0,0] [0+0+0 800 0+0+0] [0+0+0 600 0+0+0] [BFC] children: not-inline
  BlockContainer <html> at [0,0] positioned [0+0+0 400 0+0+400] [0+0+0 200 0+0+0] [BFC] children: not-inline
    Box <body> at [0,0] positioned flex-container(row) [0+0+0 60 0+0+0] [0+0+0 40 0+0+0] [FFC] children: not-inline
      BlockContainer <div.child> at [0,0] flex-item [0+0+0 30 0+0+0] [0+0+0 40 0+0+0] [BFC] children: not-inline
        BlockContainer <div.content> at [0,0] [0+0+0 60 0+0+-30] [0+0+0 40 0+0+0] children: not-inline
      BlockContainer <(anonymous)> (not painted) [BFC] children: inline
        TextNode <#text> (not painted)

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 400x200]
    PaintableBox (Box<BODY>) [0,0 60x40]
      PaintableWithLines (BlockContainer<DIV>.child) [0,0 30x40]
        PaintableWithLines (BlockContainer<DIV>.content) [0,0 60x40]

SC for Viewport<#document> [0,0 800x600] (z-index: auto)
 SC for BlockContainer<HTML> [0,0 400x200] (z-index: auto)
