Viewport <#document> at (0,0) content-size 800x600 children: not-inline
  BlockContainer <html> at (0,0) content-size 800x466 [BFC] children: not-inline
    Box <body> at (8,8) content-size 500x450 [GFC] children: not-inline
      BlockContainer <div.a> at (8,183) content-size 500x0 [BFC] children: not-inline
      BlockContainer <div.b> at (8,183) content-size 500x0 [BFC] children: not-inline
      BlockContainer <(anonymous)> (not painted) [BFC] children: inline
        TextNode <#text>

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 800x466]
    PaintableBox (Box<BODY>) [8,8 500x450]
      PaintableWithLines (BlockContainer<DIV>.a) [8,58 500x125]
      PaintableWithLines (BlockContainer<DIV>.b) [8,183 500x175]
