Reduce Margin between Tabs and Title Bar in Firefox Australis

[Update] For convenience the script has been added to userstyles.org.

Australis has been incorporated to release channel since Firefox 29, replacing title bar with tabs bar. One thing to be picky about is that there is a margin above tabs and it wastes vertical space.

Solution 1

In Stylish add-on (https://addons.mozilla.org/en-US/firefox/addon/stylish/), create a new user script with the following content:

:root[sizemode="normal"] #titlebar {
  margin-bottom: -60px !important;
}

and the gap will be removed.

Solution 2

With some further search I found this post: http://forums.mozillazine.org/viewtopic.php?f=23&t=2813465 where "Gingerbread Man" posted another solution that is shorter but produces the same outcome:

#TabsToolbar { margin-top: 0px !important; }

I prefer this solution.

Outcome

Before:

Firefox 29 Australis has a margin above tabs.

After:

The margin is removed.