anchor.diff:    bool release() {
       if (_WatchList._isEmpty(this) && _LinkedList._isEmpty(this)) {
         _releaseWatch();
  -      // Remove ourselves from cache, or else new registrations will go to us,
  -      // but we are dead
   
         if (forwardingHandler != null) {
           // TODO(misko): why do we need this check?
  
positive.code:   /**
     * Create a new child [WatchGroup].
     *
     * - [context] if present the the child [WatchGroup] expressions will evaluate
     * against the new [context]. If not present than child expressions will
     * evaluate on same context allowing the reuse of the expression cache.
     */
    WatchGroup newGroup([Object context]) {
      _EvalWatchRecord prev = _childWatchGroupTail._evalWatchTail;
  
negative.code: 
    /** [ChangeDetector] used for field watching */
    final ChangeDetectorGroup<_Handler> _changeDetector;
    final RootWatchGroup _rootGroup;
  
    /// STATS: Number of field watchers which are in use.
  