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layer at (0,0) size 800x50
  RenderBlock {HTML} at (0,0) size 800x50
    RenderBody {BODY} at (8,16) size 784x18
      RenderBlock {P} at (0,0) size 784x18
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          text run at (0,0) width 503: "Try selecting some text in this document. It should be have a green background."