title: How to debug a Thunderbird addon/extension's JavaScript
body: <p>I want to develop a Thunderbird 12 addon. I have written a simple JS function. (File: "chrome\content\myApp.js"). This file is called by a xul-'onclick'-event. I have packed my addon as a .xpi file and then I have installed it. (All ok, it's working!)</p>
  
  <p>Now I'd like to debug my JS functions. But I can't find a working JS Debugger. 
  I have tried this addons:</p>
  
  <ul>
  <li>"Javascript Debugger"(0.9.89). Not working: The thread doesn't stop at my breakpoints.</li>
  <li>Firebug(1.7.2) + Chromebug(1.7.2). Not working: I can't enable the JS debug tab. (<strong>Update</strong>: I also can't set/change a "context")</li>
  </ul>