I'm using twitter bootstrap to create a button group.
When I changed font size of smaller class to 12px (14px by default), the height of the left button grows 1px. How can I avoid it? Checked by Chrome 26, Firefox 20.

```
<div class="btn-group">
  <button class="btn">
    Foo
    <div class="smaller" style="font-size: 12px;">
      Smaller
    </div>
  </button>
  <button class="btn">
    Bar
  </button>
</div>

```

Example is available at <http://jsfiddle.net/kawachi/xkP9j/>