//inspiré de http://code.google.com/p/analytics-api-samples/source/browse/trunk/src/tracking/javascript/v5/social/ga_social_tracking.js
var _ga = _ga || {};
var _gaq = _gaq || [];
_ga.trackSocial = function(opt_pageUrl, opt_trackerName) {
  _ga.trackFacebook(opt_pageUrl, opt_trackerName);
};

_ga.trackFacebook = function(opt_pageUrl, opt_trackerName) {
  var trackerName = _ga.buildTrackerName_(opt_trackerName);
  try {
    if (FB && FB.Event && FB.Event.subscribe) {
      FB.Event.subscribe('edge.create', function(targetUrl) {
        _gaq.push([trackerName + '_trackSocial', 'facebook', 'like',
            targetUrl, opt_pageUrl]);
      });
      FB.Event.subscribe('edge.remove', function(targetUrl) {
        _gaq.push([trackerName + '_trackSocial', 'facebook', 'unlike',
            targetUrl, opt_pageUrl]);
      });
      FB.Event.subscribe('message.send', function(targetUrl) {
        _gaq.push([trackerName + '_trackSocial', 'facebook', 'send',
            targetUrl, opt_pageUrl]);
      });
    }
  } catch (e) {}
};

_ga.buildTrackerName_ = function(opt_trackerName) {
  return opt_trackerName ? opt_trackerName + '.' : '';
};