layer at (0,0) size 800x600
  RenderCanvas at (0,0) size 800x600
layer at (0,0) size 800x50
  RenderBlock {HTML} at (0,0) size 800x50 [bgcolor=#00FF00]
    RenderBody {BODY} at (8,16) size 784x18
      RenderBlock {P} at (0,0) size 784x18
        RenderText {TEXT} at (0,0) size 314x18
          text run at (0,0) width 314: "The background of the document should be green"
