nsIProcess2 in Firefox 3.5

 Executes the file this object was initialized with optionally calling
 an observer after the process has finished running.
 @param args       An array of arguments to pass to the process in the
                   native character set.
 @param count      The length of the args array.
 @param observer   An observer to notify when the process has completed. It
                   will receive this process instance as the subject and
                   "process-finished" or "process-failed" as the topic. The
                   observer will be notified on the main thread.
 @param holdWeak   Whether to use a weak reference to hold the observer.