code: public static void register (PerformanceObserver obs, String name, long delta)
      {
          // get the observer's action hashtable
          Map<String, PerformanceAction> actions = _observers.get(obs);
          if (actions == null) {
              // create it if it didn't exist
              _observers.put(obs, actions = Maps.newHashMap());
          }
  
          // add the action to the set we're tracking
          actions.put(name, new PerformanceAction(obs, name, delta));
      }
docs: Register a new action with an observer, the action name, and the milliseconds to wait
  between checkpointing the action's performance.
  
  @param obs the action observer.
  @param name the action name.
  @param delta the milliseconds between checkpoints.