layer at (0,0) size 800x600
  RenderCanvas at (0,0) size 800x600
layer at (0,0) size 800x600
  RenderFlexibleBox {HTML} at (0,0) size 800x600 [bgcolor=#FFFFFF]
    RenderFlexibleBox {BODY} at (0,0) size 800x600 [color=#FFFFFF] [bgcolor=#008000]
      RenderBlock (anonymous) at (0,0) size 450x600
        RenderText {TEXT} at (0,0) size 450x18
          text run at (0,0) width 450: "You should see white text on a green background that fills the window."
        RenderText {TEXT} at (0,0) size 0x0