fontconfig 2.12 in 18.04 causes firefox to freeze when launching chrome

[Jason Pleau]

fontconfig version: 2.12.6-0ubuntu2

Related:

https://askubuntu.com/questions/1076412/firefox-freezing-with-100-cpu-usage-for-30-seconds-when-launching-chromium

https://bugzilla.mozilla.org/show_bug.cgi?id=1495900

https://bugzilla.mozilla.org/show_bug.cgi?id=1411338

Steps to reproduce:

1) Launch firefox, open a few tabs

2) Launch chrome

3) Go back to firefox, and notice it starts being very slow, switching tabs do nothing (the content area remains blank).

4) Backport fontconfig 2.13 from cosmic to bionic

5) Try to reproduce 1-3, be happy because it is now working fine!

I backported 2.13.0-5ubuntu3 from cosmic to bionic, if that helps. I don't have the right setup right now to do a bisect from upstream or from debian patches sadly.

~ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.2 LTS
Release: 18.04
Codename: bionic

[Sebastien Bacher (seb128)]

Thank you for your bug report. The issue seems similar to https://bugzilla.mozilla.org/show_bug.cgi?id=1495900

[Launchpad Janitor (janitor)]

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

[Olivier Duclos (odc)]

Any chance fontconfig 2.13 could be backported to bionic? This is a seriously annoying issue.