title: localStorage.getItem, localStorage.setItem functions don't work in Chrome extension ported to Firefox
body: <p>I have developed Chrome extension.</p>
  
  <p>In this extension, I used <code>localStorage.getItem</code>, <code>localStorage.setItem</code> functions to save some data.</p>
  
  <p>After that, I converted Chrome extension to Firefox add-on.
  In this case, I couldn't set, get some data into <code>localStorage</code>:</p>
  
  <pre><code>localStorage.getItem("data"); //it returns NULL
  </code></pre>
  
  <p>I hope that i will get solution here.
  Thanks</p>