Display defaults back to 200% on external screen connection

[Pedro Côrte-Real]

I have a 2560x1440 screen that by default gets set to 200% which is way too large. I just set it to 100% and tweak the font scaling a bit instead. This is equivalent to the 1.38 scaling that used to be available in settings in 16.04.

When connecting an external 1920x1080 screen the settings revert back to 200% on the internal screen. This makes no sense. The internal screen hasn't changed its properties so there's no real reason to change to 200% just because there's a second screen attached. Particularly since the setting is per-screen.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: gnome-control-center 1:3.28.1-0ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-22.24-generic 4.15.17
Uname: Linux 4.15.0-22-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.1
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Thu May 31 21:02:32 2018
InstallationDate: Installed on 2018-05-31 (0 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
SourcePackage: gnome-control-center
UpgradeStatus: No upgrade log present (probably fresh install)