feat: add feature targeting for styles to tab-related packages

[crisbeto]

Adds support for style feature targeting to the tab, tab-bar, tab-indicator and tab-scroller packages.

[codecov-io]

Codecov Report

Merging #4838 into master will increase coverage by 0.29%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4838      +/-   ##
==========================================
+ Coverage   98.97%   99.27%   +0.29%     
==========================================
  Files         130      130              
  Lines        6347     6347              
  Branches      821      821              
==========================================
+ Hits         6282     6301      +19     
+ Misses         64       45      -19     
  Partials        1        1

Impacted Files	Coverage Δ
packages/mdc-checkbox/component.ts	96.87% <0%> (+1.04%)	⬆️
packages/mdc-tab/component.ts	98.36% <0%> (+3.27%)	⬆️
packages/mdc-base/component.ts	100% <0%> (+3.57%)	⬆️
packages/mdc-ripple/component.ts	100% <0%> (+3.77%)	⬆️
packages/mdc-auto-init/index.ts	100% <0%> (+4.16%)	⬆️
packages/mdc-ripple/util.ts	97.56% <0%> (+4.87%)	⬆️
packages/mdc-tabs/tab/component.ts	100% <0%> (+5%)	⬆️
packages/mdc-switch/component.ts	98.27% <0%> (+6.89%)	⬆️
packages/mdc-radio/component.ts	95.83% <0%> (+8.33%)	⬆️

---

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 e8afc42...91f0dc9. Read the comment docs.

[crisbeto]

cc @mmalerba

[crisbeto]

@abhiomkar @mmalerba I've reworked it based on the feedback.

[mmalerba]

Can you give a diff of the final CSS just to sanity check? Code looks good to me

[crisbeto]

Sure, here's the before and after. The main difference is that the order of a few selectors has changed, but from what I could tell it shouldn't have an effect on the end result. Also the after styles are a bit smaller, because the current ones in master include an extra license header in the middle of the file.

before.zip
after.zip

[mmalerba]

Most of the look pretty trivial, though mdc.tab.css has some significant movement (maybe that's finem just wanted to point it out: http://www.mergely.com/53ydf5dw/)

[crisbeto]

I've reworked it based on the latest set of feedback: I got rid of the smaller private mixins and the ones that are left should have feature targets. Can you take another look @abhiomkar?

[abhiomkar]

LGTM. Thanks @crisbeto!