Example of using the W3C Resource Timing API to display the resource timing information of +1 buttons. This code can be pasted into the Javascript console in Chrome on any page.

plus_one_rt.js

(function() {
  // request PerformanceResourceTiming info for all resources on the page
  var resources = window.performance.getEntriesByType('resource');

  // filter all resources to just +1 button iframes with timing information
  var p1Resources = resources.filter(function(rtInfo) {
    return rtInfo.name.indexOf('_/+1/fastbutton') != -1 &&
           rtInfo.responseStart != 0;
  });

  // describes the timing information for a resource
  var rtReport = function(rtInfo) {
    var preRequestTime = Math.round(rtInfo.requestStart - rtInfo.startTime);
    var requestTime = Math.round(rtInfo.responseStart - rtInfo.requestStart);
    var responseTime = Math.round(rtInfo.responseEnd - rtInfo.responseStart);
    var duration = Math.round(rtInfo.duration);
    return 'Pre-Request Time: ' + preRequestTime + 'ms\n' +
           'Request Time: ' + requestTime + 'ms\n' +
           'Response Time: ' + responseTime + 'ms\n' +
           'Total Duration: ' + duration + 'ms\n';
  };

  // report the timing for the first +1 button in the list, if one exists
  if (p1Resources.length > 0) {
    alert('First +1 button timing information:\n\n' + rtReport(p1Resources[0]));
  } else {
    alert('no widgets with resource timing information found');
  }
})();