Firefox 28 doesn't use intl.accept_languages defined in syspref.js

[Cs-gon]

We have system-wide settings defined in /etc/firefox/syspref.js, amongst others the intl.accept_languages option to define the accept languages for our environment.

Firefox 28 (28.0+build2-0ubuntu0.12.04.1) doesn't use the accept languages (and maybe others options) defined in syspref.js, when sending the HTTP header, even though the intl.accept_language value shown in about:config is correct (same as in syspref.js).

It only works, if the intl.accept_languages is defined as a lockPref in syspref.js, which we don't want, because the users should be able to customize the setting. But we need to explicitly set the "de-de" accept language.

This worked in previous Firefox versions (e.g. 27 or older).

the corresponding line in syspref.js is:
pref("intl.accept_languages", "de-de,de,en-us,en");

about:config shows:
intl.accept_languages = "de-de,de,en-us,en"

accept languages, which are sent in HTTP Header (this is the default from the firefox-locale-de package) :
"de,en-us,en"

[Cs-gon (cs-gon)]

I have to correct something:

It seems older Firefox versions had the same problem, but it wasn't obvious, because the default accept_languages of the firefox-locale-de package were already "de-de,de,en-us,en". In Firefox 28 the default was changed to "de,en-us,en".

Nevertheless the problem is still, that Firefox reads the setting from syspref.js and displays this correctly in about:config, but doesn't use this value when constructing the HTTP header. The problem seems to be this test: http://mxr.mozilla.org/mozilla-central/source/modules/libpref/src/nsPrefBranch.cpp#232

So the accept_languages will only be used, when they are set by a user pref, or a locked pref, but not with a "simple" pref in syspref.js.