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- Add rules to autogenerate Polymer3 versions of
  cr_policy_pref_behavior and cr_policy_pref_indicator at build time
- Autogenerate tests for the Polymer 3 version of
  cr_policy_pref_indicator.

This will be used to migrate the chrome://settings page in future.

Bug: 1042558
Change-Id: I4721c7c4ae9d898135fea09111dcc6c79b529888
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2021335Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735694}