prototype(slider): create prototype slider based on MDC web

[devversion]

Creates a prototype of mat-slider that uses MDC web. The feature comparison document has been filled.

A list of notable bugs in the MDC foundation right now:

• input event not rounded before comparing (causing multiple input events; workaround applied)
• Thumb label not updating if value changes programmatically (workaround applied)
• Slider updates value with right mouse events
• change event always fired on mouse up or keydown
• slider measurements and ticks only updated on init and "resize" event
  • standard Angular Material slider did this on mouseenter.
• Vertical alignment (incorrect calculations; currently shifted down 2px of baseline)

Notable feature differences:

• Visually sliders look totally different to our current implementation
• Vertical sliders are not supported (yet?)
• Sliders do not support decimal steps.
• Sliders cannot be inverted (no support in the foundation)

Currently blocked on #16772.

[mmalerba]

I think MDC is planning to redo the slider at some point because the visual style has updated in the spec. If they're planning to also revisit the API and supported features at that time it may make sense to wait on this one.

@abhiomkar do you know if there are any plans to change the API when updating the visual style?

[devversion]

@mmalerba I had a look at their slider branch which I assumed was for the mentioned rework and it looked like most of the things remained the same and just a few public-facing foundation/adapter changes were done.

Happy to wait for the rework to land though. I just didn't think the rework will happen anytime soon and if it lands, we can re-use this work as most of the things should remain the same.

https://github.com/material-components/material-components-web/commits/feat/slider (last commit Aug 2018; unless there is a different branch)

[abhiomkar]

Slider refactor is not planned in this quarter.

[mmalerba]

Ok, sounds like we can just go ahead with this for now

[jelbourn]

File a bug on their repo?

[devversion]

Looks like it's by intention that they don't respect modifier keys. Native range sliders don't seem to respect these either (i.e. value still changes with SHIFT + LEFT ARROW).

How should we proceed? based on their implementation of the keyboard logic we can't overwrite/configure this behavior.

[devversion]

@jelbourn Feedback addressed. Created the issues on the MDC repository and updated the feature comparison doc accordingly.

[mmalerba]

Should be unblocked now that the chips changes are in

[devversion]

Yes. thanks @mmalerba for updating the label.

[devversion]

@jelbourn can you have another look at this PR when you get a chance?

[jelbourn]

LGTM, minor comments

[jelbourn]

LGTM

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