Migrate //rlz from base::Callback to base::OnceCallback

This updates //rlz to use base::OnceCallback instead of legacy
base::Callback. No intended functional change is included.

This reduces the number of 'base::Bind' in //rlz from 3 to 0,
as tracked at http://goo.gl/LUVhDj

Bug: 714018
Change-Id: I4a016a47acfae635ff4ed0c3b2f22c0ca62b8f5c
Reviewed-on: https://chromium-review.googlesource.com/952729
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541697}
1 file changed