fire when both properties change

MapSearchController.js

ready: function () {
  var content = this.get('content'),
    gmap = this.get('map.gmap');

  return content && gmap;
}.property('controllers.map.gmap', 'content'), 

drawSearchResults: function () {
  var self = this,
    marker,
    content = this.get('content'),
    map = this.get('map'),
    gmap = map.get('gmap');
 
  content.forEach(function (item, index, enumerable) {
    item.setMap(gmap);
    self.bindMarker(item);
 
    if (enumerable.length === 1) {
      gmap.setCenter(item.getPosition());
      map.send('openBuildingByMarker', item);
    }
  });
}.observes('ready'),