GitLab

Original algorithm: choose the active policy provider with the highest
   priority and apply all policies from it.

Updated algorithm: for each policy, find the highest priority provider
 that has defined value, and returns that policy.

Bug: 1134303
Change-Id: I3461f476e5404f97a08a6a83f57346804e84e678
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2443541Reviewed-by: Sorin Jianu <sorin@chromium.org>
Reviewed-by: S. Ganesh <ganesh@chromium.org>
Commit-Queue: Xiaoling Bao <xiaolingbao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813449}