[TextEditor] Folding screen background rendered wrong.

Folding screen background ends on previous line, when last line of FoldSegment ends with <eof>.
![screen shot 2014-12-05 at 2 30 05 am](https://cloud.githubusercontent.com/assets/1479065/5309822/81cc004a-7c32-11e4-919e-b10ef4bdc13c.png)

Should be:
![screen shot 2014-12-05 at 2 30 42 am](https://cloud.githubusercontent.com/assets/1479065/5309823/84d4e914-7c32-11e4-8d5f-3f36d854d047.png)