Viewport <#document> at (0,0) content-size 800x600 children: not-inline
  BlockContainer <html> at (0,0) content-size 800x116 [BFC] children: not-inline
    Box <body> at (8,8) content-size 400x100 flex-container(row) [FFC] children: not-inline
      Box <div.outer> at (8,8) content-size 200x100 flex-container(column) flex-item [FFC] children: not-inline
        BlockContainer <div.upper> at (8,8) content-size 200x200 flex-item [BFC] children: not-inline
          BlockContainer <div.spacer> at (8,8) content-size 200x200 children: not-inline
        BlockContainer <div.lower> at (8,208) content-size 200x18 flex-item [BFC] children: inline
          frag 0 from TextNode start: 0, length: 3, rect: [8,208 26.953125x18] baseline: 13.796875
              "whf"
          TextNode <#text>

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 800x116] overflow: [0,0 800x226]
    PaintableBox (Box<BODY>) [8,8 400x100] overflow: [8,8 400x218]
      PaintableBox (Box<DIV>.outer) [8,8 200x100] overflow: [8,8 200x218]
        PaintableWithLines (BlockContainer<DIV>.upper) [8,8 200x200]
          PaintableWithLines (BlockContainer<DIV>.spacer) [8,8 200x200]
        PaintableWithLines (BlockContainer<DIV>.lower) [8,208 200x18]
          TextPaintable (TextNode<#text>)
