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layer at (0,0) size 800x600
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          RenderBlock {DIV} at (0,0) size 756x28
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              text run at (0,0) width 71: "This is "
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              text run at (71,0) width 106: " some text."
selection is CARET:
start:      position 8 of child 1 {TEXT} of child 1 {DIV} of child 2 {DIV} of root {DIV}
upstream:   position 8 of child 1 {TEXT} of child 1 {DIV} of child 2 {DIV} of root {DIV}
downstream: position 0 of child 2 {TEXT} of child 1 {DIV} of child 2 {DIV} of root {DIV}
