I would even allow myself to claim it's a P2 from the perseptive of the project :)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4b840a9c1e16e0fe278b9517af4e6b5f8365d176

commit 4b840a9c1e16e0fe278b9517af4e6b5f8365d176
Author: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
Date: Tue Sep 18 14:46:52 2018

[BrowserSwitcher] Expand env-vars in command-line

Environment variables on the command-line (alternative browser path and
parameters) are expanded before being passed to the external program.

On Windows, this means strings like '%HOME%' are expanded.

On Linux, this means strings like '$VAR' and '${VAR}' are expanded. Also, a '~'
at the beginning of a command-line argument is expanded to the HOME environment
variable.

Bug:  882520 
Change-Id: I9822b465999b3515d37e882f18a19df39b3e64d6
Reviewed-on: https://chromium-review.googlesource.com/1225854
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Commit-Queue: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592036}
[modify] https://crrev.com/4b840a9c1e16e0fe278b9517af4e6b5f8365d176/chrome/browser/browser_switcher/alternative_browser_driver_linux.cc
[modify] https://crrev.com/4b840a9c1e16e0fe278b9517af4e6b5f8365d176/chrome/browser/browser_switcher/alternative_browser_driver_unittest.cc
[modify] https://crrev.com/4b840a9c1e16e0fe278b9517af4e6b5f8365d176/chrome/browser/browser_switcher/alternative_browser_driver_win.cc
[modify] https://crrev.com/4b840a9c1e16e0fe278b9517af4e6b5f8365d176/chrome/browser/chrome_content_browser_client.cc