layer at (0,0) size 800x600
  RenderView at (0,0) size 800x600
layer at (0,0) size 800x600
  RenderBlock {HTML} at (0,0) size 800x600
    RenderBody {BODY} at (8,8) size 784x584
      RenderText {#text} at (20,2) size 491x18
        text run at (20,2) width 491: " This checkbox should look 50% transparent and should be in the mixed state."
      RenderText {#text} at (0,0) size 0x0
layer at (12,11) size 13x13
  RenderBlock {INPUT} at (4,3) size 13x13