GitLab

xdg-open's man page says:
> xdg-open is for use inside a desktop session only.

Use the DISPLAY environment variable to detect this.

Updates #19131.

Change-Id: I3926b3e1042393939b2ec6aacd9b63ac8192df3b
Reviewed-on: https://go-review.googlesource.com/37390

Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>