After you enable the the preference "Show my windows and tabs from last time" - browser.startup.page=3 - browser.warnOnQuit should be changed to false to avoid any user misunderstanding, even if the preference is ignored in this case. This should be done also at Fx startup.
Is this still wanted?
Created attachment 456214 [details] [diff] [review]
Frankly, I'm not quite sure if this is the right place to do this, but at least it works.
I don't think this makes much sense. What would make sense is to make it easier to understand what the pref means by renaming it e.g. to browser.warnOnQuitIfTabsWontBeRestored, but that's probably not worth it...
Comment on attachment 456214 [details] [diff] [review]
Also, even if we would want this, letting every window observe the pref like this wouldn't be the right way to do it.
invalid due to Bug 592822?
(In reply to comment #3)
Well, I must agree with you. You can WONTFIX.
Wanted behavior was achieved with Bug 629485