Style completion panel when using Nimbus LAF

Before vs. After:

![style-completion-before](https://cloud.githubusercontent.com/assets/4236689/3788086/d7b6ad6e-1a50-11e4-8141-96ca1e2f1e4d.png)![style-completion-after](https://cloud.githubusercontent.com/assets/4236689/3788087/db3dd7e6-1a50-11e4-90ab-39d06667551a.png)

/cc @Manindra29