constructor(resourceIds = [], generateBundles) {
    this.resourceIds = resourceIds;
    this.generateBundles = generateBundles;
    this.onChange(true);
  }
@param {Array<String>} resourceIds     - List of resource IDs
@param {Function}      generateBundles - Function that returns a
                                         generator over FluentBundles

@returns {Localization}