Bug#723560: iceweasel can't run two sessions simultaneously

[Zefram]

Package: iceweasel
Version: 17.0.8esr-1~deb7u1
Severity: normal

Suppose one already has Iceweasel running.  Now run it again by typing
"firefox" in a terminal window on the same X screen.  A new Iceweasel
window pops up, but the second firefox process terminates immediately
instead of waiting for the end of the session with the new window.
In fact, the two Iceweasel windows are not only being managed by the
same instance of the program, they're actually treated as part of the
same session, and things done with one window will affect the other:
changes to preferences (such as preferred background colour) in one
window affect the other, and selecting the "Quit" menu option in one
window will close both.  Finally, closing the original Iceweasel window
(by an X "delete window" request) won't terminate the original firefox
process -- the process stays around to manage the second window.

I realise that managing both windows with the same process is intentional,
and done for performance reasons, but merging state of the two sessions
and losing the usual correspondence between processes and sessions
is an undesirable side effect.  I don't mind waiting the extra second
it takes to start a fresh session rather than add a new window to the
existing session.

If it's desired to have a way to open a new window in an existing session
from the command line, which I can see being useful to some people,
then that should be an option, not mandatory.  In fact, the iceweasel(1)
man page already advertises such an option ("-new-window"); it appears
that it's being treated as always on.

It gets worse.  With one Iceweasel running, if you try to run another
one on a *different* X screen then the second "firefox" invocation fails
to bring up a browser window at all.  It instead produces a small window
titled "Close Iceweasel", containing a road-sign-like icon and the text

	Iceweasel is already running, but is not responding. To open a
	new window, you must first close the existing Iceweasel process,
	or restart your system.

and an "OK" button.  Clicking on that button terminates the new process
without ever bringing up a real browser window.

The iceweasel(1) man page also advertises an option "-no-remote"
that looks as though it should decouple Iceweasel sessions, fixing the
above problems.  Empirically, if the option is used for either or both
invocations of Iceweasel, the effect is actually to yield the "Close
Iceweasel" window for the second invocation, regardless of whether it's
on the same or different X screen.

This bug report is essentially a revival of Bug#617362.  That ticket got
closed without actually being resolved, due to confusion with the related
but distinct Bug#617361 that was deemed not-a-bug.  See also Bug#187138
concerning nearly-identical behaviour of Galeon, and Bug#668850 concerning
related behaviour of Libreoffice.

-zefram