When key-kill-mode is enabled, Conkeror will stop handling application keybindings such as "C-x b" etc.
Conkeror will appear to be locked up, with no error messages in the console. Scrolling with the mouse
will however still work. "conkeror -f unfocus" will display a message in the minibuffer but does not
solve the problem.

I have reproduced the problem on xulrunner versions 25, 26 and 29a1-2014-01-29, without RC files and with
a fresh profile.

Steps to reproduce:
1. Run "conkeror -q"
2. M-x require("key-kill")
3. M-x key-kill-mode
4. Conkeror will no longer respond to keypresses.
5. No errors in the console