[Slider] focus is not saved on slider after click

[zhdanouskikh]

When clicking on slider focus should be saved on slider for enabling it for keyboard manipulation. But if navigation to slider by tab key, it has focus and keyboard is working on it.

• This is not a v0.x issue.
• I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior 🤔

1. click on slider
2. focus is on slider, slider is highlighted with focused styles

Current Behavior 😯

1. click on slider
2. focus is not on slider

Steps to Reproduce 🕹

Link: https://codesandbox.io/s/mj32kjkr6x

1. click on slider
2. focus is not set on slider after click

Context 🔦

I would like to have focus on slider after click to have an ability to manipulate with slider by keyboard. It's working now only if you reach slider by tab key.

Your Environment 🌎

Tech	Version
Material-UI	v3.6.0
Material-UI Lab	v3.0.0-alpha.24
React	v16.8.1
Browser	Google Chrome v 73.0.3683.8 (64bit)

[eps1lon]

Proposal is following WAI-ARIA Authoring Practices 1.1.

Might be enough to set focus imperatively in the click handler. We need to explore how this should behave with touch devices.

[jztang]

I'd like to work on this if no one else is! I tried out the slider with my touchscreen laptop, and touching the slider thumb does not set focus to it. Should it?