title: Consistent Empty Data using MediaRecorderAPI, intermittently
body: <p>I have a simple setup for Desktop Capturing using html5 libraries. 
  This includes a simple webpage and a chrome-extension. I am using</p>
  
  <ol>
  <li>Extension to get the sourceId</li>
  <li>Using the sourceId I call navigator.mediaDevices.getUserMedia to get the MediaStream</li>
  <li>This MediaStream is then fed into an instance of MediaRecorder for recording.</li>
  </ol>
  
  <p>This setup works most of the times, but a few times I see that requestData() on MediaRecorder instance returns blob with empty data consistently. I am clueless as to what can cause a running setup to start misbehaving sometimes. </p>
  
  <p>Some weird behaviour that I noticed in the bad state:</p>
  
  <ol>
  <li>When I try to close/refresh the window it doesn't respond. </li>
  <li>The MediaStreamTrack object in Step 2) above is 'live' but as soon as I go to Step 3) it becomes 'muted'.</li>
  <li>There's no pattern to it, sometimes it even happens when I request for the MediaStreams the very first time(which rules out the possibility that there could be some dangling resources eating up the contexts)</li>
  </ol>
  
  <p>Is there anything that I am doing wrong and am unaware of? Any help/pointers would be highly appreciated!</p>