nsIThreadObserver Interface

 This method is called (from nsIThread::ProcessNextEvent) after an event
 is processed.  This method is only called on the target thread.

 @param thread
   The thread that processed another event.
 @param recursionDepth
   Indicates the number of calls to ProcessNextEvent on the call stack in
   addition to the current call.

void afterProcessNextEvent(in nsIThreadInternal thread, in unsigned long recursionDepth)

 This interface provides the observer with hooks to implement a layered
 event queue.  For example, it is possible to overlay processing events
 for a GUI toolkit on top of the events for a thread:

   var NativeQueue;
   Observer = {
     onDispatchedEvent(thread) {
       NativeQueue.signal();
     }
     onProcessNextEvent(thread, mayWait, recursionDepth) {
       if (NativeQueue.hasNextEvent())
         NativeQueue.processNextEvent();
       while (mayWait && !thread.hasPendingEvent()) {
         NativeQueue.wait();
         NativeQueue.processNextEvent();
       }
     }
   };

 NOTE: The implementation of this interface must be threadsafe.
 
 NOTE: It is valid to change the thread's observer during a call to an
       observer method.


 This method is called after an event has been dispatched to the thread.
 This method may be called from any thread. 

 @param thread
   The thread where the event is being dispatched.

void onDispatchedEvent(in nsIThreadInternal thread)

 This method is called (from nsIThread::ProcessNextEvent) before an event
 is processed.  This method is only called on the target thread.

 @param thread
   The thread being asked to process another event.
 @param mayWait
   Indicates whether or not the method is allowed to block the calling
   thread.  For example, this parameter is false during thread shutdown.
 @param recursionDepth
   Indicates the number of calls to ProcessNextEvent on the call stack in
   addition to the current call.

void onProcessNextEvent(in nsIThreadInternal thread, in boolean mayWait, in unsigned long recursionDepth)