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This CL creates a new cr-radio-button element with the MD-refresh spec.
This CL also replaces all paper-radio-button within Settings with
cr-radio-button.

Most of the cr-radio-button's functionalities and styles are encapsulated
in separate files in a shared location, so that the controlled-radio-button
element in settings can reuse them.

There will be a follow-up CL to then replace all of paper-radio-button's
usage outside of Settings.

Bug: 840527
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I4fc47fa0b8186b5d6ef0a3b678cc68bbc58a8e3d
Reviewed-on: https://chromium-review.googlesource.com/1053299
Commit-Queue: Scott Chen <scottchen@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558620}