Viewport <#document> at (0,0) content-size 800x600 children: not-inline
  BlockContainer <html> at (0,0) content-size 800x316 [BFC] children: not-inline
    BlockContainer <body> at (8,8) content-size 784x300 children: not-inline
      BlockContainer <input.btn> at (13,10) content-size 290x296 children: not-inline
        BlockContainer <(anonymous)> at (13,10) content-size 290x296 flex-container(column) [FFC] children: not-inline
          BlockContainer <(anonymous)> at (13,149.5) content-size 290x17 flex-item [BFC] children: inline
            frag 0 from BlockContainer start: 0, length: 0, rect: [36.75,149.5 242.5x17] baseline: 13
            BlockContainer <span> at (36.75,149.5) content-size 242.5x17 inline-block [BFC] children: inline
              frag 0 from TextNode start: 0, length: 31, rect: [36.75,149.5 242.5x17] baseline: 13
                  "Should be located in the center"
              TextNode <#text>
      BlockContainer <(anonymous)> at (8,308) content-size 784x0 children: inline
        TextNode <#text>

ViewportPaintable (Viewport<#document>) [0,0 800x600]
  PaintableWithLines (BlockContainer<HTML>) [0,0 800x316]
    PaintableWithLines (BlockContainer<BODY>) [8,8 784x300]
      PaintableWithLines (BlockContainer<INPUT>.btn) [8,8 300x300]
        PaintableWithLines (BlockContainer(anonymous)) [13,10 290x296]
          PaintableWithLines (BlockContainer(anonymous)) [13,149.5 290x17]
            PaintableWithLines (BlockContainer<SPAN>) [36.75,149.5 242.5x17]
              TextPaintable (TextNode<#text>)
      PaintableWithLines (BlockContainer(anonymous)) [8,308 784x0]
