chrome-specific padding for the compat selector (bug 1093936)

## Old

https://www.dropbox.com/s/koula33kr2qqnww/Screenshot%202014-12-02%2014.30.20.png?dl=0

## New

![screen shot 2014-12-02 at 2 40 51 pm](https://cloud.githubusercontent.com/assets/674727/5272407/71c8f9c6-7a31-11e4-8249-a6d1b349258d.png)

It's hacky, but it seems to work.
I copied it from transonic...and back then I must have copied it from a solution online. I'm not sure, I think I wrote it in the middle of Alaska offline back then.