Viewport <#document> at (0,0) content-size 800x600 children: not-inline
  BlockContainer <html> at (0,0) content-size 800x600 [BFC] children: not-inline
    BlockContainer <body> at (8,8) content-size 784x17 children: not-inline
      Box <div.grid-container> at (8,8) content-size 784x17 [GFC] children: not-inline
        BlockContainer <div.grid-item> at (8,8) content-size 392x17 [BFC] children: inline
          frag 0 from TextNode start: 0, length: 3, rect: [8,8 21.609375x17] baseline: 13.296875
              "1fr"
          TextNode <#text>

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 800x600]
    PaintableWithLines (BlockContainer<BODY>) [8,8 784x17]
      PaintableBox (Box<DIV>.grid-container) [8,8 784x17]
        PaintableWithLines (BlockContainer<DIV>.grid-item) [8,8 392x17]
          TextPaintable (TextNode<#text>)
