title: chrome.extension.getBackgroundPage() returns null after awhile
body: <p>When my chrome extension loads on chrome startup, everything seems to be ok and chrome.extension.getBackgroundPage() returns the right value (lunched from popup.js). But after awhile (2-3 minutes), especially if the browser is let alone, the function returns null. Only closing and re-opening chrome solves the problem.
  I tried to manipulate it by:</p>
  
  <pre><code>if (chrome.extension.getBackgroundPage() == null) window.location.reload(true);
  </code></pre>
  
  <p>As suggested at <a href="https://stackoverflow.com/questions/7971566/chrome-extension-getbackgroundpage-returns-null-why">Why does chrome.extension.getBackgroundPage() return null?</a>, which sometimes helps, but most of the times it just keeps refreshing the app so that chrome must be closed.
  Does anybody have an idea what could be wrong?</p>