[Slider] focus animation bug

[catamphetamine]

http://www.material-ui.com/#/components/slider
When moving a slider its "breathing" animation has a bug: sometimes it works, sometimes it doesn't (grab, move, release, grab, move, release)

[oliviertassinari]

Looks like an issue with the focus handling. I can reproduce it on mobile.
What environnement are you using?

[catamphetamine]

I'm on Chrome, Hackint0sh

[oliviertassinari]

We plan on migrating the component to the v1-beta branch. I'm closing the issue for #4793.