[SRU] system tray flashes consistently with HiDPI screens

[fossfreedom]

below - preparation for a potential SRU

[Impact]

 * upstream bug report: https://github.com/budgie-desktop/budgie-desktop/issues/1397
   System tray icons flashes rapidly and consistently on HiDPI based screens.

 * This revises the existing patch which resolved corrupt system tray icons on standard
   resolution screens. The upstream revision both fixes the original issue and
   in addition fixes the adverse side effect of this issue.

[Test Case]

 * The original bug showing black backgrounds on system tray icons could be reproduced by logging out and logging in several times or suspending and resuming several times.
   The bug could also be seen by rebooting and logging in. This also needed
   several reboots to reproduce the issue.

 * Add to your autostart applications an application that displays its icon in the
   system tray such as HexChat.
   Change the panel to either Dynamic or transparent. This will highlight clearly the original
   black background issue.
 * To test, both logout and login several times (10x) and reboot and login (10x). Also suspend and resume several times.
   System tray icons should be displayed correctly without any flashing effects nor
   black backgrounds.
 * At least two confirmations are required - once test confirmation is required from a
   user with a standard resolution screen (i.e. vertical screen resolution 1024 or less)
   The second confirmation required is a user using a HiDPI based screen (i.e. vertical screen resolution of 1500px or higher)

[Regression Potential]

 * The most likely regression here is that the original black background
   display issue for system tray icons would reoccur.
 * The resolution in this case would be to move the panel from top-to-bottom or visa-versa.

[Other Info]

 * N/A

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: budgie-desktop 10.4+git20171031.10.g9f71bb8-1.2ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
CurrentDesktop: Budgie:GNOME
Date: Thu May 3 20:36:27 2018
InstallationDate: Installed on 2016-11-26 (522 days ago)
InstallationMedia: budgie-remix 16.10 "Budgie-remix" - amd64 (20161013)
PackageArchitecture: all
SourcePackage: budgie-desktop
UpgradeStatus: Upgraded to bionic on 2018-04-14 (18 days ago)

[fossfreedom (fossfreedom)]

marking as invalid - doesnt appear to be any call to backport this.