title: Persistently looping CAAnimations
body: <p>A <code>CAAnimation</code> may be looped by setting its <code>repeatCount</code> to <code>CGFLOAT_MAX</code>. Following some events, however, the animation will be removed and won't be restored automatically. For example:</p>
  
  <ul>
  <li>When application enters background: The animation must be re-added
  manually when returning from background.</li>
  <li>When navigating away from the controller: In some cases the animation
  won't be restored after popping from the stack.</li>
  </ul>
  
  <p>My general question is: What events cause animations to be removed; how do I ensure that they are re-added?</p>