title: google maps v3 zoom_changed event does not fire when zoom changes
body: <p>I have a v3 Google map being loaded exactly as I expect and the marker does what I intend. However when I change the zoom, the zoom_changed event that I have added does not appear to fire. Would anyone be able to shed any light on why? My code is below.</p>
  
  <pre><code>function map_initialise() {
      var mapCentre = new google.maps.LatLng(53.75, -1.50);
      var mapOptions = {
          zoom: 6,
          center: mapCentre,
          mapTypeId: google.maps.MapTypeId.HYBRID
      }
  
      var map = new google.maps.Map(document.getElementById('map_canvas'), mapOptions);
  
      var latlong1 = new google.maps.LatLng(52.456550,1.680182);
      var windowtext1 = 'Some text';
      var popup1 = new google.maps.InfoWindow({
          content: windowtext1
      });
      var marker1 = new google.maps.Marker({
          position: latlong1,
          title: "Some text"
      });
      google.maps.event.addListener(marker1, 'click', function() { 
          popup1.open(map,marker1);
      });
      marker1.setMap(map);
  }
  
  google.maps.event.addDomListener(window, 'load', map_initialise);
  
  google.maps.event.addListener(map, 'zoom_changed', function() {
      setTimeout(reCentre, 3000);
  });
  
  function reCentre() {
      var newcentre = new google.maps.LatLng(53.000,0.000);
      map.panTo(newcentre);
  }
  </code></pre>