GitLab

Display configurator will not configure mirror pairs between devices (see
AllDisplaysOnSameDevice() in ui/display), so remove code attempting to
support this.

Bug: 851997
Test: hardware mirroring on cros

Change-Id: Ie2fdc9f42423be1cd8efe7c59d43001e6096e935
Reviewed-on: https://chromium-review.googlesource.com/1104858
Commit-Queue: Michael Spang <spang@chromium.org>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569971}