constructor(compilationOptions, pluginOptions) {
      super({objectMode: true});

      this.compilationOptions_ = compilationOptions;
      this.pluginName_ = pluginOptions.pluginName || PLUGIN_NAME;
      this.logger_ = pluginOptions.logger || (message => console.info(message));

      this.fileList_ = [];
    }
@return {function(Object<string>=, Object<string>=):Object}