code: function repeatTaskForAllLocales(taskName, dependencies, operation) {
    return ALL_LOCALES.map((locale) => {
      // Convert build-js-$ to build-js-fr, for example.
      const replaceTokens = (name) => name.replace(/\$/g, locale);
      const localeTaskName = replaceTokens(taskName);
      const localeDependencies = dependencies.map(replaceTokens);
      gulp.task(localeTaskName, gulp.series(
          gulp.parallel.apply(null, localeDependencies),
          () => operation(locale)
      ));
      return localeTaskName;
    });
  }
docs: Repeats a gulp task for all locales.
  @param {string} taskName The gulp task name to generate. Any $ tokens will be
  replaced with the language code (e.g. build-$ becomes build-fr, build-es,
  etc.).
  @param {!Array<string>} dependencies The gulp tasks that each operation
  depends on. Any $ tokens will be replaced with the language code.
  @param {function()} operation The function to execute.
  @return {!Array<string>} The list of generated task names.