anchor.diff:      editorFontSize = new JsonPreference<num>(_jsonStore, "editorFontSize");
       keyBindings = new JsonPreference<String>(_jsonStore, "keyBindings");
   
  -    // Check to see if we need to migrate any old store preferences to JSON.
  -    onPreferencesReady = _jsonStore.whenLoaded.then((_) {
  -      if (_jsonStore.firstRun) {
  -        return Future.wait([_migrateFromStore("aceTheme", "editorTheme"),
  -            _migrateFromStore("fontSize", "editorFontSize"),
  -            _migrateFromStore("keyBindings", "keyBindings"),
  -
  -        ]);
  -      }
  -    });
  -  }
  -
  -  Future _migrateFromStore(String oldKey, String newKey) {
  -    return prefsStore.getValue(oldKey, null).then((String value) {
  -      if (value != null) _jsonStore.setValue(newKey, value);
  -    });
  +    onPreferencesReady = _jsonStore.whenLoaded;
     }
   }
   
  
positive.code:   Map _userMap;
  
    PreferenceStore _persistentStore;
    Future<bool> whenLoaded;
    bool _loaded = false;
  
    // TODO: implement isDirty
    bool get isDirty => null;
  
    bool _firstRun = false;
    bool get firstRun => _firstRun;
  
    Stream<PreferenceEvent> get onPreferenceChange => _changeConroller.stream;
    StreamController<PreferenceEvent> _changeConroller = new StreamController();
  
negative.code:   }
  
    Future _loadUserPrefs() {
      return _persistentStore.getValue("userJsonPrefs", "{}")
          .then((String json) {
        _userMap = JSON.decode(json);
      });
    }
  