nsIKeygenThread
  This is used to communicate with the thread generating a key pair,
  to be used by the dialog displaying status information.
[scriptable, uuid(8712a243-5539-447c-9f47-8653f40c3a09)]
interface nsIKeygenThread : nsISupports

Methods

 startKeyGeneration - run the thread
   A user interface using this interface needs to
   call this method as soon as the status information
   is displaying. This will trigger key generation.
   To allow the closure of the status information,
   the thread needs a handle to an observer.

   observer will be called on the UI thread.
   When the key generation is done, the observe method will
   be called with a topic of "keygen-finished" and null data
   and subject.
void startKeyGeneration(in nsIObserver observer) 
 userCanceled - notify the thread
   If the user canceled, the thread is no longer allowed to
   close the dialog. However, if the thread already closed
   it, we are not allowed to close it.
void userCanceled(out boolean threadAlreadyClosedDialog)