Keyboard `tab` event on Firefox

Hi,
On `Firefox 57.0.1`, if I use `tab` key in a React Input with floating label, the event navigates the focus to the "floating label" element of that field instead of the next input field. I believe what's happening is that it is going to the next element after the input which in this case is the floating label. 

On chrome this is working fine. Let me know if you need more info.
