Bug#825325: firefox-esr: Firefox sometimes uses a bold font when it shouldn't

[Ben Longbons]

Package: firefox-esr
Version: 45.1.1esr-1+b1
Severity: normal

Dear Maintainer,

After installing some new fonts, Firefox now displays most web pages in
bold - particularly, any site that requests "Arial".

This is *not* reproduced when I call font-config directly, so Firefox
must be doing something funky.

The package `fonts-arkpandora` contains Aerial, which is the highest
priority Arial--compatible font available in Debian. If I call
`fc-match Arial`, it correctly returns the "Regular" variant of the
font. However, Firefox is choosing the "Bold" variant for some reason.

If I remove /etc/fonts/conf.d/61-arkpandora.conf then Firefox chooses
the next option, Arimo, and correctly chooses the non-Bold variant.

I have reproduced this all with a fresh firefox profile
(firefox -no-remote -P).

-- Package-specific info:

-- Extensions information
Name: Default theme
Location: /usr/lib/firefox-esr/browser/extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}.xpi
Package: firefox-esr
Status: enabled

Name: Firefox Hello Beta
Location: ${PROFILE_EXTENSIONS}/loop at mozilla.org.xpi
Status: enabled

Name: HTTPS-Everywhere
Location: ${PROFILE_EXTENSIONS}/https-everywhere-eff at eff.org
Status: enabled

Name: It's All Text!
Location: ${PROFILE_EXTENSIONS}/itsalltext at docwhat.gerf.org
Status: enabled

Name: Reddit Enhancement Suite
Location: ${PROFILE_EXTENSIONS}/jid1-xUfzOsOFlzSOXg at jetpack.xpi
Status: enabled

Name: Shumway
Location: ${PROFILE_EXTENSIONS}/shumway at research.mozilla.org
Status: app-disabled

Name: uBlock Origin
Location: ${PROFILE_EXTENSIONS}/uBlock0 at raymondhill.net.xpi
Status: enabled

Name: xkcd #1288: Substitutions (Cloud To Butt Fork)
Location: ${PROFILE_EXTENSIONS}/substitutions at github.com.xpi
Status: user-disabled

-- Plugins information

-- Addons package information
ii  firefox-esr    45.1.1esr-1+b1 amd64        Mozilla Firefox web browser - Extended Support Release (ESR)

-- System Information:
Debian Release: stretch/sid
  APT prefers testing-debug
  APT policy: (600, 'testing-debug'), (600, 'testing'), (500, 'unstable-debug'), (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.5.0-2-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages firefox-esr depends on:
ii  debianutils               4.7
ii  fontconfig                2.11.0-6.4
ii  libasound2                1.1.0-1
ii  libatk1.0-0               2.20.0-1
ii  libc6                     2.22-9
ii  libcairo2                 1.14.6-1+b1
ii  libdbus-1-3               1.10.8-1
ii  libdbus-glib-1-2          0.106-1
ii  libevent-2.0-5            2.0.21-stable-2+b1
ii  libffi6                   3.2.1-4
ii  libfontconfig1            2.11.0-6.4
ii  libfreetype6              2.6.3-3+b1
ii  libgcc1                   1:6.1.1-4
ii  libgdk-pixbuf2.0-0        2.34.0-1
ii  libglib2.0-0              2.48.1-1
ii  libgtk2.0-0               2.24.30-1.1
ii  libhunspell-1.4-0         1.4.1-2
ii  libnspr4                  2:4.12-2
ii  libnss3                   2:3.23-2
ii  libpango-1.0-0            1.40.1-1
ii  libsqlite3-0              3.12.2-1
ii  libstartup-notification0  0.12-4
ii  libstdc++6                6.1.1-4
ii  libvpx3                   1.5.0-3
ii  libx11-6                  2:1.6.3-1
ii  libxcomposite1            1:0.4.4-1
ii  libxdamage1               1:1.1.4-2+b1
ii  libxext6                  2:1.3.3-1
ii  libxfixes3                1:5.0.1-2+b2
ii  libxrender1               1:0.9.9-2
ii  libxt6                    1:1.1.5-1
ii  procps                    2:3.3.11-3
ii  zlib1g                    1:1.2.8.dfsg-2+b1

Versions of packages firefox-esr recommends:
ii  gstreamer1.0-libav         1.8.1-1
ii  gstreamer1.0-plugins-good  1.8.1-1

Versions of packages firefox-esr suggests:
ii  fonts-lmodern          2.004.5-3
ii  fonts-stix [otf-stix]  1.1.1-4
ii  libcanberra0           0.30-3
ii  libgnomeui-0           2.24.5-3.1
ii  libgssapi-krb5-2       1.13.2+dfsg-5
pn  mozplugger             <none>

-- no debconf information