title: Canvas recording using captureStream and mediaRecorder
body: <p>How can i record streams from more than one canvas?
  ie, when i change one canvas to other it has to record the active canvas continue to the first.</p>
  
  <p>I have done like this:</p>
  
  <pre><code>stream = canvas.captureStream();
  mediaRecorder = new MediaRecorder(stream, options);
  mediaRecorder.ondataavailable = handleDataAvailable;
  mediaRecorder.start(10);
  
  function handleDataAvailable(event) {
    recordedBlobs.push(event.data);
  }
  </code></pre>
  
  <p>But when adding another stream, only the first part is recorded. I'am pushing recorded data to a global array.</p>