op shelf landing changes for tablets (bug 1067432)

With 1 app:
![](http://f.cl.ly/items/0F0P2e2O0J410E1R091s/Image%202014-09-16%20at%201.56.21%20PM.png)

With > 1 app:
![](http://f.cl.ly/items/371k1k3O2V0T1q41041l/Image%202014-09-16%20at%202.05.51%20PM.png)
This is the very thing they're complaining about. We're requiring that they give us two images to spec, so there should be no fallback necessary. (Since the wrong-sized image is what started this.)