Viewport <#document> at (0,0) content-size 800x600 children: not-inline
  BlockContainer <html> at (0,0) content-size 800x216 [BFC] children: not-inline
    Box <body> at (8,8) content-size 784x200 [GFC] children: not-inline
      Box <section> at (8,8) content-size 784x200 flex-container(row) [FFC] children: not-inline

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 800x216]
    PaintableBox (Box<BODY>) [8,8 784x200]
      PaintableBox (Box<SECTION>) [8,8 784x200]
