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] [0+0+0 800 0+0+0] [0+0+0 123 0+0+0] [BFC] children: not-inline
    BlockContainer <body> at [8,8] [8+0+0 784 0+0+8] [8+0+0 107 0+0+8] children: not-inline
      BlockContainer <div.upper> at [8,8] [0+0+0 784 0+0+0] [0+0+0 16 0+0+75] children: inline
        frag 0 from TextNode start: 0, length: 5, rect: [8,8 46.15625x16] baseline: 12.796875
            "upper"
        TextNode <#text> (not painted)
      BlockContainer <div.mystery> at [8,99] [0+0+0 784 0+0+0] [0+0+0 0 0+0+0] children: not-inline
      BlockContainer <div.lower> at [8,99] [0+0+0 784 0+0+0] [0+0+0 16 0+0+0] children: inline
        frag 0 from TextNode start: 0, length: 5, rect: [8,99 43.359375x16] baseline: 12.796875
            "lower"
        TextNode <#text> (not painted)

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 800x123]
    PaintableWithLines (BlockContainer<BODY>) [8,8 784x107]
      PaintableWithLines (BlockContainer<DIV>.upper) [8,8 784x16]
      PaintableWithLines (BlockContainer<DIV>.mystery) [8,99 784x0]
      PaintableWithLines (BlockContainer<DIV>.lower) [8,99 784x16]

SC for Viewport<#document> [0,0 800x600] (z-index: auto)
 SC for BlockContainer<HTML> [0,0 800x123] (z-index: auto)
