title: Mutation Observer not firing
body: <p>Hi I'm building a chrome extension. I have a javascript file in which I want to detect changes to a div on facebook.com so I attach it to a mutation observer. The thing is now if I navigate to another page on Facebook say by clicking the home button the mutation observer stops working even though a div by the same id is present in this new page. It only starts working once I refresh the page. Any ideas on how I can fix this?</p>
  
  <p>Also all my code is wrapped in a document.ready jquery function so I would assume that would automatically fire when I navigate to a new facebook page by clicking the home button but that doesn't happen. It only fires when I either explicitly type the url or refresh the page after navigating. </p>
  
  <p>The code is like this:</p>
  
  <pre><code>    $ (document).ready( function() {
  
    var observeDOM = (function(){
        var MutationObserver = window.MutationObserver || window.WebKitMutationObserver,
            eventListenerSupported = window.addEventListener;
  
        return function(obj, callback){
            if( MutationObserver ){
                // define a new observer
                var obs = new MutationObserver(function(mutations, observer){
                    if( mutations[0].addedNodes.length || mutations[0].removedNodes.length )
                        callback();
                });
                // have the observer observe foo for changes in children
                obs.observe( obj, { childList:true, subtree:true });
            }
            else if( eventListenerSupported ){
                obj.addEventListener('DOMNodeInserted', callback, false);
                obj.addEventListener('DOMNodeRemoved', callback, false);
            }
        }
    })();
  
  
    if (document.getElementById('contentArea') !== null) {
      console.log("working");
      observeDOM( document.getElementById('contentArea') ,function(){
  
          console.log("DOM CHANGED");
  
      });
    }
  });
  </code></pre>
  
  <p>UPDATE: Seems like the problem is with how facebook loads pages (see: <a href="https://stackoverflow.com/questions/4120647/how-facebook-load-pages">How facebook load pages?</a>)</p>
  
  <p>Any way to detect these individual changes happening via AJAX?</p>