anchor.diff:  ///
   /// A [Registry] object caches objects found using the [lookup]
   /// method, or added using [add], and returns the same object every time
  -/// they are requested.
  +/// it is requested.
   /// A different [Registry] object that works on the same underlying registry,
   /// will not preserve the identity of elements
   ///
  
positive.code:   // also copying the cache.
    static final Expando<_RegistryCache> _caches = Expando<_RegistryCache>();
  
    /// Port for sending command to the central registry manager.
    final SendPort _commandPort;
  
    /// Create a registry linked to a [RegistryManager] through [commandPort].
  
negative.code: /// See [SendPort] for details on the restrictions on objects which can be sent
  /// between isolates.
  ///
  /// A registry can be used to make a number of objects available to separate
  /// workers in different isolates, for example ones created using
  /// [IsolateRunner], without sending all the objects to all the isolates.
  /// A worker can then request the data it needs, and it can add new data
  