Chrome Version       : 69.0.3497.81 (Build officiel) Built on Ubuntu , running on LinuxMint 18.2 (64 bits)
URLs (if applicable) :
Other browsers tested:
  Firefox - OK (62.0 (64 bits))
  Vivaldi - OK (1.15.1147.64 (Stable channel) (64 bits))
have tested this issue:
     Safari: 
    Firefox: yes
       Edge:
    Vivaldi: yes

What steps will reproduce the problem?
(1) open chromium
(2) start any audio content, like youtube
(3) in pavucontrol, change audio chanel of Chromium from default to any other one
(4) stop playing sound in chromium or restart it
(5) the audio chanel of Chromium is reset to default

What is the expected result?
Chromium should remember the audio channel to use as it does before and as does any other browser and applications with pavucontrol.

What happens instead?
Chromium always reset audio channel to use to the default one.

Please provide any additional information below. Attach a screenshot if
possible.
I get it from last update. I have no error in logs in /var/log/kern.log.

Start-Date: 2018-09-14  00:12:47
Commandline: /usr/sbin/synaptic --hide-main-window --non-interactive --parent-window-id 81788955 -o Synaptic::closeZvt=true --progress-str Veuillez patienter, cela peut prendre un certain temps --finish-str La mise à jour est terminée --set-selections-file /tmp/tmpvere1q82
Requested-By: mysterty (1000)
Upgrade: nodejs:amd64 (8.11.4-1nodesource1, 8.12.0-1nodesource1), skypeforlinux:amd64 (8.29.0.50, 8.30.0.50), initramfs-tools-bin:amd64 (0.122ubuntu8.11, 0.122ubuntu8.12), adobe-flashplugin:amd64 (1:20180814.1-0ubuntu0.16.04.2, 1:20180911.1-0ubuntu0.16.04.1), chromium-browser:amd64 (68.0.3440.106-0ubuntu0.16.04.1, 69.0.3497.81-0ubuntu0.16.04.1), firefox-locale-en:amd64 (61.0.1+linuxmint1+sylvia, 62.0+linuxmint4+sylvia), firefox-locale-fr:amd64 (61.0.1+linuxmint1+sylvia, 62.0+linuxmint4+sylvia), chromium-codecs-ffmpeg-extra:amd64 (68.0.3440.106-0ubuntu0.16.04.1, 69.0.3497.81-0ubuntu0.16.04.1), code:amd64 (1.27.1-1536226049, 1.27.2-1536736588), firefox:amd64 (61.0.1+linuxmint1+sylvia, 62.0+linuxmint4+sylvia), chromium-browser-l10n:amd64 (68.0.3440.106-0ubuntu0.16.04.1, 69.0.3497.81-0ubuntu0.16.04.1), initramfs-tools-core:amd64 (0.122ubuntu8.11, 0.122ubuntu8.12), initramfs-tools:amd64 (0.122ubuntu8.11, 0.122ubuntu8.12)
End-Date: 2018-09-14  00:14:20

Start-Date: 2018-09-14  02:43:40
Commandline: /usr/sbin/synaptic --hide-main-window --non-interactive --parent-window-id 81788955 -o Synaptic::closeZvt=true --progress-str Veuillez patienter, cela peut prendre un certain temps --finish-str La mise à jour est terminée --set-selections-file /tmp/tmp0d76lrbj
Requested-By: mysterty (1000)
Install: linux-modules-4.15.0-34-generic:amd64 (4.15.0-34.37~16.04.1, automatic), linux-headers-4.15.0-34:amd64 (4.15.0-34.37~16.04.1), linux-image-4.15.0-34-generic:amd64 (4.15.0-34.37~16.04.1), linux-headers-4.15.0-34-generic:amd64 (4.15.0-34.37~16.04.1), linux-modules-extra-4.15.0-34-generic:amd64 (4.15.0-34.37~16.04.1)
End-Date: 2018-09-14  02:48:58