chore(slider): reduce scss specificity

[moog16]

related: #1687

[codecov-io]

Codecov Report

Merging #2158 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2158   +/-   ##
=======================================
  Coverage   99.25%   99.25%           
=======================================
  Files          84       84           
  Lines        3768     3768           
  Branches      489      489           
=======================================
  Hits         3740     3740           
  Misses         28       28

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e01bb84...bb1f27f. Read the comment docs.

[williamernest]

LGTM

[kfranqueiro]

You are moving mixin invocations which rely on & to an @at-root selector, which means the & is now nothing. e.g. .mdc-slider:not(.mdc-slider--disabled) .mdc-slider__track becomes just :not(.mdc-slider--disabled) .mdc-slider__track which will apply to every MDC Slider instance because :not(...) will match any parent of the slider track whatsoever.

This change is not safe to make and I think we should close this PR.

[kfranqueiro]

Confirmed, this breaks disabled styles.

What it should look like:

What it looks like in this PR:

Closing this, since the only change this makes causes a regression.