fix(linear-progress): Add aria attributes to linear progress bar to support screen readers

[rbuckheit]

fix(linear-progress) support aria attributes

Adds aria attributes to MDC Linear progress to support screen readers.

BREAKING CHANGE: Adds new adapter methods to MDCLinearProgressAdapter.

[codecov-io]

Codecov Report

Merging #5248 into master will increase coverage by 0.28%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #5248      +/-   ##
==========================================
+ Coverage   98.63%   98.91%   +0.28%     
==========================================
  Files         122      122              
  Lines        6002     6011       +9     
  Branches      774      774              
==========================================
+ Hits         5920     5946      +26     
+ Misses         81       64      -17     
  Partials        1        1

Impacted Files	Coverage Δ
packages/mdc-linear-progress/foundation.ts	100% <100%> (ø)	⬆️
packages/mdc-linear-progress/component.ts	96.96% <100%> (+0.41%)	⬆️
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-switch/component.ts	98.27% <0%> (+6.89%)	⬆️
packages/mdc-radio/component.ts	95.83% <0%> (+8.33%)	⬆️

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[joyzhong]

Looks great! Please add a BREAKING CHANGE message to the description per https://github.com/angular/angular/blob/master/CONTRIBUTING.md#footer, since we're adding two adapter methods.

Also create the equivalent CL in google3. I will merge this in when that CL is ready to go.

[abhiomkar]

LGTM.

Please make sure to include BREAKING CHANGE: line in your commit message, when you squash & merge so that it'll appear nicely in our CHANGELOG :)

[rbuckheit]

LGTM.

Please make sure to include BREAKING CHANGE: line in your commit message, when you squash & merge so that it'll appear nicely in our CHANGELOG :)

Squashed and added that to the commit message :-)