Issue 4528: Break in non-selected tab leaves Firebug broken

Steps to reproduce

  1. Enable and switch to the Script panel
  2. Open another tab in Firefox and load http://getfirebug.com in it
  3. Open Firebug for it
  4. Switch back to this tab
  5. Click the button Break delayed
  6. Before the timer runs out switch to the other tab again

Expected Results