Screensaver not suppressed when watching full screen video

[Alan Pope 🍺🐧🐱 🦄]

Using chromium 59 on an up to date 17.10 and watching a full screen video, the screensaver kicks in after 5 minutes. It should be suppressed. This only happens in chrome/chromium. Firefox is unaffected. Unfortunately my TV provider doesn't support Firefox, so I have to use Chrome.

Steps to reproduce.

In Settings -> Power -> Set Blank screen to 5 minutes
Open chromium
Play a long video such as https://www.youtube.com/watch?v=jX6kn9_U8qk
Full screen (and optionally mute) the video
Leave computer alone

Expected result

10 hours of video plays

Actual result

After 5 minutes, the screen goes blank

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: chromium-browser 59.0.3071.109-0ubuntu1.1360
ProcVersionSignature: Ubuntu 4.11.0-10.15-generic 4.11.8
Uname: Linux 4.11.0-10-generic x86_64
NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
ApportVersion: 2.20.6-0ubuntu4
Architecture: amd64
CurrentDesktop: GNOME
DRM.card0-DP-1:
 enabled: disabled
 dpms: Off
 status: disconnected
 edid-base64:
 modes:
DRM.card0-DP-2:
 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-eDP-1:
 enabled: enabled
 dpms: On
 status: connected
 edid-base64: AP///////wAw5AYEAAAAAAAXAQSVHxF46tyVo1hVoCYNUFQAAAABAQEBAQEBAQEBAQEBAQEBujaArHA4JEA8JDUANa8QAAAaAAAAAAAAAAAAAAAAAAAAAAAAAAAA/gBMRyBEaXNwbGF5CiAgAAAA/gBMUDE0MFdGMS1TUEoxAHk=
 modes: 1920x1080
Date: Mon Aug 7 14:24:55 2017
Desktop-Session:
 'ubuntu-wayland'
 'None'
 'None'
DetectedPlugins:

Env:
 'None'
 'None'
InstallationDate: Installed on 2017-08-02 (4 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Alpha amd64 (20170712)
InstalledPlugins:
 /usr/lib/mozilla/plugins:
   => libgnome-shell-browser-plugin.so
         (size: 18920 bytes, mtime: Sun Jul 23 18:08:04 2017)
Load-Avg-1min: 0.54
Load-Processes-Running-Percent: 0.1%
MachineType: LENOVO 20BV001BUK
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.11.0-10-generic.efi.signed root=UUID=20b4dfc6-b888-4543-b51f-3346a19a0e18 ro quiet splash vt.handoff=7
SourcePackage: chromium-browser
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 01/27/2016
dmi.bios.vendor: LENOVO
dmi.bios.version: JBET56WW (1.21 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20BV001BUK
dmi.board.vendor: LENOVO
dmi.board.version: 0B98417 WIN
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.modalias: dmi:bvnLENOVO:bvrJBET56WW(1.21):bd01/27/2016:svnLENOVO:pn20BV001BUK:pvrThinkPadT450:rvnLENOVO:rn20BV001BUK:rvr0B98417WIN:cvnLENOVO:ct10:cvrNone:
dmi.product.name: 20BV001BUK
dmi.product.version: ThinkPad T450
dmi.sys.vendor: LENOVO
modified.conffile..etc.default.chromium-browser: [deleted]

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Strangiato Xanadu (strangiato)]

I can confirm this problem on Arch running Chromium 60 or chromium-based browsers (Opera and Vivaldi) under Gnome Wayland session. No problem under X11.
I think it's some problem between Chromium and Wayland because the same problem affects the same browsers under KDE Plasma Wayland session.

[Boris Erdmann (boris-erdmann)]

Or maybe the caffeine just doesn't work with wayland?