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- Autogenerate Polymer 3 version of cr-radio-button and its style and
  behavior
- Add closure targets
- Autogenerate and run cr-radio-button automated tests with Polymer 3
- Add to demo page

Bug: 965770
Change-Id: Ie625c10ad8776d4875dd1202bca8a0b788bf3bb9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1773746Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691834}