title: Error 'open' called on an object that does not implement interface XMLHttpRequest
body: <p>I get this error when I'm trying to launch an ajax request inside of a class from another class function.
  You can get the error in firefox console from this example:</p>
  
  <p><a href="https://jsfiddle.net/d2o1d0eu/" rel="nofollow">https://jsfiddle.net/d2o1d0eu/</a></p>
  
  <p><a href="http://codepen.io/anon/pen/dGwwKG" rel="nofollow">http://codepen.io/anon/pen/dGwwKG</a></p>
  
  <pre><code>var MyClass = new Class({
  
      initialize: function(options){
  
          this.my_request = new Request({
              url: '/echo/html/',
              method: 'post',
              onSuccess: function(resp) {
                  alert(resp);
              }
          });
  
      },
  
      request: function(param){
  
          this.my_request.send('html='+param);
  
      }   
  
  });
  
  var MySecondClass = new Class({
  
      Implements: [Options],
  
      options: {
          first_class: {}
      },
  
      initialize: function(options){
  
          this.setOptions(options);
  
          this.options.first_class.request('internal'); // error
  
      },
  
      request: function(param){
  
          this.options.first_class.request(param);
  
      }
  
  });
  
  var unknown_name = new MyClass();
  // unknown_name.request('unknown_name test'); // ok
  
  var test = new MySecondClass({
  
      'first_class': unknown_name
  
  });
  
  // test.request('second class test'); // error
  </code></pre>
  
  <p>Any suggestion is appreciated, thanks.</p>