Unexpected visual element in a simple Tab layout

The screen shot below is of a simplified version of t开发者_运维问答he application from the Tab Layout tutorial. You can see a black horizontal line below the tabs. Why is it there and how can I remove it?

Try removing the android:padding attribute from the FrameLayout. If you want padding around everything but the top then you'll have to use the padding/Left/Right/Bottom attributes.

I think that line results from how the tabs are implemented. If you look at one of my questions about a strange black line I found that it was an artifact of the ActivityGroup that I was using. This is the same widget that tabs use.