fix(drawer): Use parentNode DOM API when selecting scrim to make it work with Shadow DOM

[abhiomkar]

Fixes #4254

[codecov-io]

Codecov Report

Merging #4265 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #4265   +/-   ##
=======================================
  Coverage   98.48%   98.48%           
=======================================
  Files         130      130           
  Lines        5736     5736           
  Branches      766      766           
=======================================
  Hits         5649     5649           
  Misses         87       87

Impacted Files	Coverage Δ
packages/mdc-drawer/index.js	97.22% <100%> (ø)	⬆️

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[mdc-web-bot]

All 758 screenshot tests passed for commit ccd2353 vs. master! 💯🎉

[acdvorak]

I think we just need a unit test for this, and then it should be good to go!

[abhiomkar]

@acdvorak Updated unit test to include test for shadow dom. PTAL.

[acdvorak]

I verified that the unit test fails with parentElement and passes with parentNode.

LGTM! Thanks Abhinay!

[mdc-web-bot]

All 621 screenshot tests passed for commit cefa3b3 vs. master! 💯🎉