Horrible scroll performance on ios theme
I was getting horrible scroll performance, and I traced it down to this rule

``` css
background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='100%' height='1'><rect fill='#c8c7cc' x='0' y='0' width='100%' height='0.5'/></svg>");
```
