Bug 1078904 - Activities menu on fullscreen_layout landscape r=mhenretty

Here is what happens without adding those lines. I know is a different bug, but I think we can just fix it here.
![2014-10-10-11-20-57](https://cloud.githubusercontent.com/assets/368225/4590445/a1850cb4-505f-11e4-87cd-3b8b22a2573c.png)