Prevent Firebug from crashing in Firefox 13 / Window 7

Summary:
Simpler fix for D2572. Not entirely sure why Firebug is crashing Firefox. It appears to be callstack depth related, possibly? You can sort of reproduce this like this:

>>> var f = function(n) { n && f(n - 1); }
>>> f(10000); // Takes a few ms to run.
>>> f(40000); // Takes a few ms to run.
>>> f(50000); // Hangs Firefox.

If there are 2,000 files, we currently hit a stack depth of around 4,000 with the pass() rules, so it seems like we should be 10x short of exploding.

Anyway, this keeps us from increasing stack depth for menus that aren't currently open and stops Firebug from crashing.

Test Plan: Clicked 2000-diff revision in Firefox.

Reviewers: vrana

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D2870