title: Why would I ever need to cancelAnimationFrame()
body: <p>I don't understand why the API includes <code>cancelAnimationFrame()</code>, because
  I can stop the animation by setting the <code>continue</code> variable like this:</p>
  
  <pre><code>function draw(timestamp) {
    if (continue == true) { requestAnimationFrame(draw); }
  }
  </code></pre>
  
  <p>So the questions is <strong>under what circumstances should I use cancelAnimationFrame()?</strong></p>