GitLab

Implement dock mac address source handler which changes shill Ethernet
property.

More details about USB Ethernet MAC address source policy
implementaion in shill: go/shill-dock-passthrough.

Bug: b:132240657
TEST=unittests and manual test that shill receive policy on changes
     and chrome startup

Change-Id: Ic3fc7dd416b60294bfcab122ebb64db7f7ea00da
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1700203Reviewed-by: Pavol Marko <pmarko@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Oleh Lamzin <lamzin@google.com>
Cr-Commit-Position: refs/heads/master@{#699742}