I have the following fiddle:
http://jsfiddle.net/q05n5v4c/2/
In Chrome, it renders just fine. The chevron is on the right side.
However, in Firefox, it
Remove the float on the span, add position: absolute to it and position it using top/right/bottom/left. Note: .btn-group already have position: relative from bootstrap.
position: absolute
position: relative
HTML
Checked option
CSS
div.btn-group span { position: absolute; top: 7px; right: 12px; }
Here's a working fiddle.