pref "general.useragent.override"

[Thu-Van Luu]

Hi,
I see this pref defined in nsHTTPHandler::InitUserAgentComponent.  But,
when I try to use it by putting it in user.js, it doesn't seem to work.
It looks like we failed the nsPref::CopyCharPref call because the pref
name wasn't in the hashtable.
Can someone else verify this for me and tell me why it's not in the hash
table. I  don't see where/when Mozilla actually reads the prefs from
user.js and put the values into the hashtable.
Appreciate  any insight on this...
Thanks,
Thu-Van.