Viewport <#document> at (0,0) content-size 800x600 children: not-inline
  BlockContainer <html> at (1,1) content-size 798x39 [BFC] children: not-inline
    Box <body.outer> at (10,10) content-size 780x21 flex-container(row) [FFC] children: not-inline
      BlockContainer <div.middle> at (11,11) content-size 202x19 flex-item [BFC] children: not-inline
        BlockContainer <div.inner> at (12,12) content-size 200x17 children: inline
          frag 0 from TextNode start: 0, length: 4, rect: [12,12 45.15625x17] baseline: 13.296875
              "OPEN"
          TextNode <#text>

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 800x41]
    PaintableBox (Box<BODY>.outer) [9,9 782x23]
      PaintableWithLines (BlockContainer<DIV>.middle) [10,10 204x21]
        PaintableWithLines (BlockContainer<DIV>.inner) [11,11 202x19]
          TextPaintable (TextNode<#text>)
