title: react native Navigator navigationBar - has 3/4 method that's never being used?
body: <p>I am looking at this file <a href="https://github.com/facebook/react-native/blob/master/Libraries/CustomComponents/Navigator/NavigatorNavigationBar.js" rel="nofollow">https://github.com/facebook/react-native/blob/master/Libraries/CustomComponents/Navigator/NavigatorNavigationBar.js</a>, have read it several times. cant seem to find where are the following methods are being used:</p>
  
  <pre><code>immediatelyRefresh
  _getReusableProps
  _updateIndexProgress
  updateProgress 
  </code></pre>
  
  <p><code>updateProgress</code> is the entry point for <code>updateIndexProgress</code> and <code>getReusableProps</code>, but i dont see anywhere in the file where its used.</p>