layer at (0,0) size 800x600
  RenderCanvas 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
      RenderBlock {DIV} at (0,0) size 784x88 [border: (2px solid #FF0000)]
        RenderText {TEXT} at (2,2) size 11x28
          text run at (2,2) width 11: "a"
        RenderBR {BR} at (0,0) size 0x0
        RenderBR {BR} at (2,30) size 0x28
        RenderText {TEXT} at (2,58) size 12x28
          text run at (2,58) width 12: "b"
      RenderBlock {DIV} at (0,88) size 784x88 [border: (2px solid #FF0000)]
        RenderText {TEXT} at (2,2) size 11x28
          text run at (2,2) width 11: "a"
        RenderBR {BR} at (0,0) size 0x0
        RenderBR {BR} at (2,30) size 0x28
        RenderBR {BR} at (2,58) size 0x28
selection is CARET:
start:      position 1 of child 4 {BR} of child 3 {DIV} of root {BODY}
upstream:   position 1 of child 4 {BR} of child 3 {DIV} of root {BODY}
downstream: position 1 of child 4 {BR} of child 3 {DIV} of root {BODY}
