[FR] Make sliders printable

[tmburnell]

Bug, feature request, or proposal:

I am not going to call this a Bug, but a feature request.
Can we find a way to make sliders printable?

What is the expected behavior?

I would like to be able to see both the line and the selector.

What is the current behavior?

Using the base slider example:

• Unchanged it will only print the circle selector with no line.
• Changed will print nothing (neither the line or the selector)

My assumption is this is due to background colors do not print.
One possible fix is use box-shadow (because i believe these are printable)

What are the steps to reproduce?

https://mndnjgqbrvd.angular.stackblitz.io/

What is the use-case or motivation for changing an existing behavior?

I have documentation pages where the slider is a completion level.
So it would be nice to be able to print the page.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

All

[mmalerba]

This would be nice to have but I don't think the core team will have time to work on it. It might be a good fix for someone to contribute