Button style on chrome differs from the rest

Button style on chrome differs from the rest

I want to style a "sign in with facebook" button using the facebook icon
in font-awesome and bootstrap
for this I have the following html
<a href="#" class="btn btn-large login_facebook">
<i class="icon-facebook"> </i> | Sign in with Facebook</a>
and adding to this the proper css
.login_facebook {
background: #6e86bd;
background: -moz-linear-gradient(top, #6e86bd 0%, #6680b9 100%);
background: -webkit-gradient(linear, 0% 0%, 0% 100%, from(#6e86bd),
to(#6680b9));
border-top: 1px solid #3f5b98;
border-left: 1px solid #3f5b98;
border-bottom: 1px solid #3f5b98;
border-right: 1px solid #3f5b98;
-moz-border-radius: 6px;
-webkit-border-radius: 6px;
border-radius: 6px;
-moz-box-shadow: inset 0 1px 0 0 #abbbdf;
-webkit-box-shadow: inset 0 1px 0 0 #abbbdf;
box-shadow: inset 0 1px 0 0 #abbbdf;
color: #fff;
font-weight: bold;
text-align: center;
text-shadow: 0 -1px 1px #344d80;
margin: 0 0 10px 0;
vertical-align: top;
position: relative;
}
.login_facebook .icon-facebook {
font-size: 37px;
vertical-align: bottom;
position: relative;
bottom: 0;
line-height: 0px;
}
on chrome the f icon is aligned with the bottom of the button but on
firefox, ie it doesn't
best seen on jsfiddle http://jsfiddle.net/KM2tS/1/
I am guessing I need to add browser specific styles here, but which
styles? and is there a way to make all browsers behave the same in this
specfic case?