title: CombineLatest first event not firing
body: <p>I want to know when my application goes offline and comes back online. I have the following events registered in <code>rxjs</code>:</p>
  
  <pre><code>const online = Rx.Observable.fromEvent(window, 'online');
  const offline = Rx.Observable.fromEvent(window, 'offline');
  
  const source = Rx.Observable.combineLatest(online, offline).map(() =&gt; navigator.onLine);
  
  source.subscribe(result =&gt; {
    console.log('I\'m online: ' + (result ? 'jup' : 'nope'));
  });
  </code></pre>
  
  <p>But, the first time I go offline the event isn't triggered allthough if I add the regular <code>addEventListener</code> events I see they're getting triggered fine: </p>
  
  <pre><code>window.addEventListener('online', () =&gt; console.log('online triggered'));
  window.addEventListener('offline', () =&gt; console.log('offline triggered'));
  </code></pre>
  
  <p>Take a look at <a href="http://jsbin.com/zegidegiba/edit?js,console" rel="noreferrer">this jsbin</a> as example, switch of your netwerk via devtools and you'll see the first time it won't log <code>I'm online: ...</code>. </p>