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 784x17.46875 children: not-inline
      BlockContainer <(anonymous)> at (8,8) content-size 784x0 children: inline
        InlineNode <details>
      ListItemBox <summary> at (37,8) content-size 755x17.46875 children: inline
        line 0 width: 114.625, height: 17.46875, bottom: 17.46875, baseline: 13.53125
          frag 0 from TextNode start: 0, length: 13, rect: [37,8 114.625x17.46875]
            "I'm a summary"
        TextNode <#text>
        ListItemMarkerBox <(anonymous)> at (8,8.234375) content-size 17x17 children: not-inline
      BlockContainer <(anonymous)> at (8,25.46875) content-size 784x0 children: inline
        TextNode <#text>

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 800x600]
    PaintableWithLines (BlockContainer<BODY>) [8,8 784x17.46875]
      PaintableWithLines (BlockContainer(anonymous)) [8,8 784x0]
        InlinePaintable (InlineNode<DETAILS>)
      PaintableWithLines (ListItemBox<SUMMARY>) [37,8 755x17.46875]
        TextPaintable (TextNode<#text>)
        MarkerPaintable (ListItemMarkerBox(anonymous)) [8,8.234375 17x17]
      PaintableWithLines (BlockContainer(anonymous)) [8,25.46875 784x0]
