I don't think this is the right path to take as it will be much more difficult than just adding the Smart Lock settings page. I'd recommend closing out this issue and simply fixing  issue 870130 .

We have time to get the real fix in for M71.

Opening this up to track the interim change of removing the Setup button, since it's getting in the user's way.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/174387d0cf9393ab22d9c7ae1438c390040f2522

commit 174387d0cf9393ab22d9c7ae1438c390040f2522
Author: James Hawkins <jhawkins@chromium.org>
Date: Thu Sep 20 19:52:32 2018

Smart Lock: Remove the setup/disable button in lockScreen settings.

When multidevice flags are turned on. This is a stop-gap measure to
prevent users from running through the deprecated Smart Lock setup flow
when in the new multidevice world.

R=khorimoto@chromium.org

Bug:  881924 
Test: none
Change-Id: Ifec2bd324e55592f14a50fe6cb5331496f010eff
Reviewed-on: https://chromium-review.googlesource.com/1236840
Reviewed-by: Tommy Li <tommycli@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: James Hawkins <jhawkins@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592914}
[modify] https://crrev.com/174387d0cf9393ab22d9c7ae1438c390040f2522/chrome/browser/resources/settings/people_page/lock_screen.html
[modify] https://crrev.com/174387d0cf9393ab22d9c7ae1438c390040f2522/chrome/browser/resources/settings/people_page/lock_screen.js