function runJsPerfTests(browser) {
  return runBrowserTests('perf', browser, 'perf').then(
      /**
       * @param {!Array<{results: !Array}>} totalResults
       */
      function(totalResults) {
        var perfData = [];
        totalResults.forEach(function(testResults) {
          perfData.push.apply(perfData, testResults.results);
        });

        return perfData;
      });
}
Runs performance regression tests and prints the results in the output.
@param {string} browser
@return {!IThenable}