Fix differences between chrome and ff

As described in https://github.com/topcoat/topcoat/issues/388
Depends on theme variable https://github.com/topcoat/theme/pull/18

Pics or it didn't happen you say ? 

![screenshot from 2013-08-31 17 55 59](https://f.cloud.github.com/assets/810040/1062453/cd0d6120-124d-11e3-8475-5a346dd4c563.png)

![screenshot from 2013-08-31 17 55 49](https://f.cloud.github.com/assets/810040/1062454/d073523e-124d-11e3-91ca-47379ae3b09a.png)