Windows Jump Lists fail for Tor Browser

This ticket is a spinoff of #6062 (moved) (which I am going to close).

Windows 7 and 8 include a jump lists feature which is used by Firefox to provide a menu of tasks that may be accessed from the Start Menu or Taskbar ("Open new tab", "Open new window", etc.) These task items fail in Tor Browser because we have disabled remoting. Similarly, clicking the main "Tor Browser" pinned item fails for the same reason if Tor Browser is already running.

For now, we should change things so we do not show the jump list items. We can do so by setting these two prefs to false:

browser.taskbar.lists.frequent.enabled browser.taskbar.lists.tasks.enabled

(we also want browser.taskbar.lists.recent.enabled = false but that is already done by default).

Also – although one would think that setting browser.taskbar.lists.enabled = false would be sufficient to turn everything off, doing that may leave old jump list menu items around. So it is better to turn off the three more specific prefs. See:

http://mxr.mozilla.org/mozilla-esr24/source/browser/modules/WindowsJumpLists.jsm#219