The `scroll-top-left' command does not scroll to the top at all (it does
scroll to the left though).

Branch: Master
OS: Fedora Linux
XULRunner version: Mozilla XULRunner 23.0 - 20130805131418

Confirmed (XULRunner 23).

Looking at the source in commands.js, it is the

    I.buffer.do_command("cmd_scrollTop");

that is failing.  I can invoke cmd_scrollTop from the minibuffer and it works, so it looks like
I.buffer.do_command() is the problem.

Temporary workaround using tjim's discovery above - change the key definitions for "M-<" and "home" in
modules/bindings/default/basic-commands.js thus:

// define_key(keymap, "M-<","scroll-top-left");
define_key(keymap, "M-<","cmd_scrollTop");

// define_key(keymap, "home","scroll-top-left");
define_key(keymap, "home","cmd_scrollTop");

cmd_scrollTop fails to update window.scrollY, therefore scroll_horiz_complete would result in undoing it.
reordering the functions in scroll-top-left fixes it.

interactive("scroll-top-left",
    "Scroll the current frame all the way to the top left",
     function (I) { scroll_horiz_complete(I.buffer, -1);
                    I.buffer.do_command("cmd_scrollTop"); });

Thank you.  Pushed.