code: function _deliverChangeRecords(observer) {
          var pendingChangeRecords = pendingChangesMap.get(observer);
          pendingChangesMap.delete(observer);
          if (!pendingChangeRecords || pendingChangeRecords.length === 0) {
              return false;
          }
          try {
              observer.call(undefined, pendingChangeRecords);
          }
          catch (e) { }
  
          _cleanObserver(observer);
          return true;
      }
docs: Implementation of the internal algorithm 'DeliverChangeRecords' described in the proposal. [Corresponding Section in ECMAScript wiki](http://wiki.ecmascript.org/doku.php?id=harmony:observe_internals#deliverchangerecords)