Viewport <#document> at (0,0) content-size 800x600 children: not-inline
  BlockContainer <html> at (0,0) content-size 800x0 [BFC] children: not-inline
    Box <body> at (8,8) content-size 31.15625x300 positioned flex-container(row) [FFC] children: not-inline
      BlockContainer <div> at (8,8) content-size 31.15625x300 flex-item [BFC] children: inline
        frag 0 from TextNode start: 0, length: 3, rect: [8,8 31.15625x18] baseline: 13.796875
            "Sup"
        TextNode <#text>

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 800x0]
    PaintableBox (Box<BODY>) [8,8 31.15625x300]
      PaintableWithLines (BlockContainer<DIV>) [8,8 31.15625x300]
        TextPaintable (TextNode<#text>)
