gptlistener.js

(function() {

  //https://developers.google.com/doubleclick-gpt/reference
  var slots = ["ad_bnr_atf_01", "ad_bnr_btf_02"], 
    slotCount = window.performance && performance.mark ? slots.length : 0;

  var boomr_ready = false;
  BOOMR = window.BOOMR || {};
  BOOMR.plugins = BOOMR.plugins || {};
  BOOMR.plugins.GPT = {
    init: function() {
      boomr_ready = true;
    },

    done: function(slotElementId) {
      if (window.performance && performance.mark && slots.indexOf(slotElementId) != -1) {
        performance.mark(slotElementId);
        slotCount--;
      }

      if (boomr_ready) {
        BOOMR.sendBeacon();
      }
    },
  	
    is_complete: function() {
      return slotCount == 0;
    }
  };

  googletag = window.googletag || {};
  googletag.cmd = googletag.cmd || [];
  googletag.cmd.push(
    function() {
      googletag.pubads().addEventListener('slotRenderEnded', 
        function(e) {
          BOOMR.plugins.GPT.done(e.slot.getSlotElementId());
        });
    });

})();