title: chrome.storage.sync undefined?
body: <p>I'm trying to use chrome storage in an extension, via a content_script, but I keep failing on </p>
  
  <pre><code>Uncaught TypeError: Cannot read property 'sync' of undefined 
  </code></pre>
  
  <p>This is my code:</p>
  
  <pre><code>testChromeStorage();
  
  function testChromeStorage() {  
      console.log("Saving");
      chrome.storage.sync.set({'value': theValue}, function() {
          message('Settings saved');
      });
      chrome.storage.sync.get("value", function (retVal) {
              console.log("Got it? " + retVal.value);
      });
  }
  </code></pre>