[snap] icon set in system dialogs doesn't always match the system default

In my Xubuntu 20.04 installation the file upload dialog displays GNOME icons rather than the icon theme I have selected in ‘Appearance’ which is 'Xfce Elementary Darker'.

Google Chrome displays the correct icon set.

A test using a live session of Lubuntu 20.04 saw the Humanity icon set being used rather than the Lubuntu default set.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: chromium-browser 79.0.3945.79-0ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-9.12-generic 5.4.3
Uname: Linux 5.4.0-9-generic x86_64
ApportVersion: 2.20.11-0ubuntu15
Architecture: amd64
CurrentDesktop: GNOME
DRM.card0-DP-1:
 enabled: enabled
 dpms: On
 status: connected
 edid-base64: AP///////wAdZRUCAQAAACoVAQSlNB544gywoldRnycKUFS/zwDRwLMAlQCBgIGKgQCBSgEBAjqAGHE4LUBYLEUACSUhAAAeAAAA/wAwMDAwMDAwMQogICAgAAAA/QA4Sx5TDwAKICAgICAgAAAA/ABFRjIyMGEKICAgICAgAGI=
 modes: 1920x1080 1680x1050 1280x1024 1280x1024 1280x1024 1440x900 1280x960 1280x800 1024x768 1024x768 1024x768 800x600 800x600 800x600 800x600 640x480 640x480 640x480 640x480 720x400
DRM.card0-HDMI-A-1:
 enabled: disabled
 dpms: Off
 status: disconnected
 edid-base64:
 modes:
DRM.card0-HDMI-A-2:
 enabled: disabled
 dpms: Off
 status: disconnected
 edid-base64:
 modes:
DRM.card0-HDMI-A-3:
 enabled: disabled
 dpms: Off
 status: disconnected
 edid-base64:
 modes:
DRM.card0-eDP-1:
 enabled: enabled
 dpms: On
 status: connected
 edid-base64: AP///////wANrsQVAAAAACgXAQSVIhN4Au8FkFRSkyklUFQAAAABAQEBAQEBAQEBAQEBAQEBXjWAlnA4FEAsHCQAWMEQAAAYAAAA/gBOMTU2SEdFLUVBQgogAAAA/gBDTU4KICAgICAgICAgAAAA/gBOMTU2SEdFLUVBQgogAB0=
 modes: 1920x1080
Date: Tue Jan 7 10:40:14 2020
DiskUsage:
 Filesystem Type Size Used Avail Use% Mounted on
 /dev/sda2 ext4 73G 14G 56G 20% /home
 tmpfs tmpfs 3.9G 156M 3.7G 4% /dev/shm
 /dev/sda2 ext4 73G 14G 56G 20% /home
InstallationDate: Installed on 2019-05-17 (235 days ago)
InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Alpha amd64 (20190517)
MachineType: Novatech N350DW
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-9-generic root=UUID=35cc812a-75e8-4a5a-83d0-bd336006d2f6 ro quiet splash vt.handoff=7
Snap.Changes: Error: command ['snap', 'changes', '--abs-time', 'chromium'] failed with exit code 1: error: no changes found
Snap.ChromeDriverVersion: ChromeDriver 79.0.3945.79 (29f75ce3f42b007bd80361b0dfcfee3a13ff90b8-refs/branch-heads/3945@{#916})
Snap.ChromiumVersion: Chromium 79.0.3945.79 snap
SourcePackage: chromium-browser
UpgradeStatus: Upgraded to focal on 2019-11-08 (59 days ago)
dmi.bios.date: 03/10/2017
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 5.12
dmi.board.asset.tag: Tag 12345
dmi.board.name: N350DW
dmi.board.vendor: Novatech
dmi.board.version: Not Applicable
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: Novatech
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr5.12:bd03/10/2017:svnNovatech:pnN350DW:pvrNotApplicable:rvnNovatech:rnN350DW:rvrNotApplicable:cvnNovatech:ct10:cvrN/A:
dmi.product.family: Not Applicable
dmi.product.name: N350DW
dmi.product.sku: Not Applicable
dmi.product.version: Not Applicable
dmi.sys.vendor: Novatech