Show cursor position on outline view

Fixes : https://github.com/dart-lang/chromedeveditor/issues/3607

Happy new week!?;
Please review when you have time. (totally fine if not accepted)
@devoncarew , @ussuri 

![image](https://cloud.githubusercontent.com/assets/756988/4887463/d2848c9e-6384-11e4-8a20-5d49c0aa2f3a.png)