title: chrome cast on chrome not sending message
body: <pre><code>if (!chrome.cast || !chrome.cast.isAvailable) {
    setTimeout(initializeCastApi, 1000);
  }
  
  function initializeCastApi() {
    var sessionRequest = new chrome.cast.SessionRequest(applicationID);
    var apiConfig = new chrome.cast.ApiConfig(sessionRequest,
      sessionListener,
      receiverListener);
    chrome.cast.initialize(apiConfig, onInitSuccess, onError);
  };
  
  function sessionListener(e) {
    //this function doenot runs firsttime
    appendMessage('New session ID:' + e.sessionId);
    session = e;
    session.addUpdateListener(sessionUpdateListener); 
    session.addMessageListener(namespace, receiverMessage);
    console.log(receiverMessage);
  }
  </code></pre>
  
  <p><code>sessionListener()</code> function doenot gets called first time.when session get updaed it gets called.Why is it so?</p>