Support routine for adding W3C user timing events to a site. Includes some basic polyfill support for browsers that don't support user timing or navigation timing (though the start time for non-navigation timing support could be improved with IE < 9 to use IE's custom start event).

user-timing-rum.js

// Support routines for automatically reporting user timing for common analytics platforms
// Currently supports Google Analytics, Boomerang and SOASTA mPulse
// In the case of boomerang, you will need to map the event names you want reported
// to timer names (for mPulse these need to be custom0, custom1, etc) using a global variable:
// rumMapping = {'aft': 'custom0'};
(function() {
var wtt = function(n, t, b) {
  t = Math.round(t);
  if (t >= 0 && t < 3600000) {
    // Google Analytics
    if (!b && window['_gaq'])
      _gaq.push(['_trackTiming', 'UserTimings', n, t]);
      
    // Boomerang/mPulse
    if (b && window['rumMapping'] && window.rumMapping[n])
      BOOMR.plugins.RT.setTimer(window.rumMapping[n], t);
  }
};
utReportRUM = function(b){
  var m = window.performance.getEntriesByType("mark");
  var lm={};
  for (i = 0; i < m.length; i++) {
    g = 'usertiming';
    if (lm[g] == undefined || m[i].startTime > lm[g])
      lm[g] = m[i].startTime;
    p = m[i].name.match(/([^\.]+)\.([^\.]*)/);
    if (p && p.length > 2 &&
        (lm[p[1]] == undefined ||
         m[i].startTime > lm[p[1]]))
        lm[p[1]] = m[i].startTime;
  }
  for (g in lm)
    wtt(g, lm[g], b);
};
utOnLoad = function() {utReportRUM(false);};
if (window['addEventListener'])
    window.addEventListener('load', utOnLoad, false);   
else if (window['attachEvent'])
    window.attachEvent('onload', utOnLoad);  

// Boomerang/mPulse support
utSent = false;
BOOMR = window.BOOMR || {};
BOOMR.plugins = BOOMR.plugins || {};
BOOMR.plugins.UserTiming = {
  init: function(config) {BOOMR.subscribe('page_ready', function(){
    if (!utSent) {
      utReportRUM(true);
      utSent=true;
      BOOMR.sendBeacon();
    }
  });},
  is_complete: function() {return utSent;}
};
})();

user-timing.js

/*
Strategically place:

markUserTime('some event');

Through your code to get measurements for when various activities complete.  It 
will also generate timeline events so you can see them in Chrome's dev tools.  

A good use case is to add them inline to sections of your site that are 
above-the fold (right after the menu, right after the main story, etc) and also 
in the onload handler for any critical above-the-fold images.
*/
;(function () {
  var w = typeof window != 'undefined' ? window : exports,
      marks = [];
  w.performance || (w.performance = {});
  w.performance.now || (
    w.performance.now = performance.now || performance.webkitNow ||
                             performance.msNow || performance.mozNow);
  if (!w.performance.now){
    var s = Date.now ? Date.now() : +(new Date());
    if (performance.timing && performance.timing)
      s = performance.timing.navigationStart
    w.performance.now = (function(){
      var n = Date.now ? Date.now() : +(new Date());
      return n-s;
    });
  }
  w.performance.mark || (
  w.performance.mark =
    w.performance.webkitMark ? w.performance.webkitMark :
    (function (l) {
      marks.push({'name':l,'entryType':'mark','startTime':w.performance.now(),'duration':0});
    }));
  w.performance.getEntriesByType || (
  w.performance.getEntriesByType =
    w.performance.webkitGetEntriesByType ? w.performance.webkitGetEntriesByType :
    (function (t) {
      return t == 'mark' ? marks : undefined;
    }));
}());
window.markUserTime = function(l) {
  var raf = window['requestAnimationFrame'] ||
    (function(callback){setTimeout(callback, 0);});
  raf(function(){
    window.performance.mark(l);
    if (window['console'] && console['timeStamp'])
      console.timeStamp(l);
  });
};

Depends on what you want to do. The 2nd one is a polyfill and support routine for user timing. The first one is a bridge that will report user timing to Google Analytics and Boomerang (or SOASTA).

You can see it live on webpagetest.org if you want to see an example.

btw, if you haven't seen it yet, this blog post has a bunch more detail: http://blog.patrickmeenan.com/2013/07/measuring-performance-of-user-experience.html

better to use setImmediate than setTimeout(0)

The new mPulse has RT and UT built in. Used your script as a basis for mine.

@bluesmoon Any chance that's open source? Or does Soasta maintain a private fork of boomerang?

@bluesmoon Also, which repo is considered stable? Your fork, or lognormal, or another?

@pmeenan Out of curiosity, why is this step necessary?

if (t >= 0 && t < 3600000) {

https://gist.github.com/pmeenan/5902672#file-user-timing-rum-js-L9

Curiously enough, I left this step out, and am getting lots of IE9 responses that appear to be a timestamp, instead of the delta.

The spec says http://www.w3.org/TR/performance-timeline/#dom-performance-getentriesbytype that getEntriesByType should always return a sequence. It seems like it would be more correct if the polyfill returned [] instead of undefined when the type is not 'mark'. https://gist.github.com/edmund-huber/d3acd4d510d895cf860a#file-user-timing-js-L39

There is a bug in line 22:

if (performance.timing && performance.timing)

should probably be

if (w.performance.timing && w.performance.timing.navigationStart)

@jamischarles, the lognormal one is stable. RT plugin is opensource. UT isn't so much a plugin, nothing really to opensource, though I'm thinking of merging it into RT.