Created attachment 345351 [details]
Screenshot across multiple webkit based browser vs Firefox gecko
CSS rule that changes background is not being applied for on a non-button element.
To reproduce, use the following example (available at https://next.plnkr.co/edit/wYsCEVvT3eJgSRre?preview) -
<div class="btn" type="submit">Hello world</div>
<button class="btn" type="submit">Hello world</div>
The div.btn does not have a red background, expected that it should have a red background.
background-color only disables appearance on actual buttons, not divs. I think this is reasonable/by design. If you want the 'none' appearance on a div, don't set it to 'button'.