Comment 1 for bug 923944

Note that we don't intentionally force this preference, but it gets overwritten due to a bug in Firefox (preferences that are changed by a user back to the upstream default after being overridden by an extension are forgotten on shutdown).

We did originally have a workaround for this, but it changed the preferences API in such a way that it completely broke Firefox Sync, causing a bogus value to be sent in the Accept-Language header - which caused major sites (including Google) to be presented in the wrong language.

We made the decision to regress this bug to fix the Firefox Sync bug instead, as we considered that bug to be much more serious than this.