Viewport <#document> at (0,0) content-size 800x600 children: not-inline
  BlockContainer <html> at (0,0) content-size 800x67 [BFC] children: not-inline
    BlockContainer <body> at (8,8) content-size 784x51 children: inline
      frag 0 from Box start: 0, length: 0, rect: [28,39 49.71875x0] baseline: 6
      Box <div.button> at (28,39) content-size 49.71875x0 flex-container(row) [FFC] children: not-inline
        BlockContainer <(anonymous)> at (28,28) content-size 49.71875x22 flex-item [BFC] children: inline
          frag 0 from TextNode start: 0, length: 5, rect: [28,28 49.71875x22] baseline: 17
              "Hello"
          TextNode <#text>

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 800x67]
    PaintableWithLines (BlockContainer<BODY>) [8,8 784x51]
      PaintableBox (Box<DIV>.button) [8,19 89.71875x40]
        PaintableWithLines (BlockContainer(anonymous)) [28,28 49.71875x22]
          TextPaintable (TextNode<#text>)
