twbs/bootstrap — pull request #11482 by Elijen (2013-11-14 13:30:36+00:00)
Title: Affix: use scrollHeight instead of offsetHeight

`document.body.offsetHeight` returns "wrong" value when the following CSS is applied:

```css
html, body {
height: 100%;
}
```

A wrong (negative) `top` value is then calculated for `affix-bottom`.