title: chrome.storage.sync undefined error
body: <p>I'm writing a simple extension and need to save user blacklisted keywords. I'm using the options_page for chrome to ask users for input, and save those words to the storage to be used later. However, when I press 'save', I get the error <code>Uncaught TypeError: Cannot read property 'sync' of undefined</code>, but I followed the instructions in the chrome extension documentation. I added <code>"permissions": ["storage"]</code>to the manifest.json file, and reloaded the extension and options page multiple times, yet I still get the same error. Here's my javascript code: </p>
  
  <pre><code>var save_options = function() {
    var blacklistWords = document.getElementById('word').value;
    chrome.storage.sync.set({'blacklistWords': blacklistWords}, function() {
      // Update status to let user know options were saved.
      alert("saved");
    });
  };
  
  document.getElementById('save').addEventListener('click', save_options);
  </code></pre>
  
  <p>I would really appreciate it if someone could help me figure this out.</p>