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This is currently not yet wired up to the android UI, but is otherwise
fully functional. There are some smaller follow-ups that I extracted
from this CL:
- Update to metrics enums
- Wiring it up to android

Bug: b/171776026
Change-Id: I7a05d97ccabb8c2bbaa3bb574d74772e9c4dbfb0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2517696
Commit-Queue: Clemens Arbesser <arbesser@google.com>
Reviewed-by: Marian Fechete <marianfe@google.com>
Cr-Commit-Position: refs/heads/master@{#825274}