title: Chrome Extension : Toggle content_script via browser_action
body: <p>How can I toggle script/content in page using browser action button?</p>
  
  <p>Example:</p>
  
  <ul>
  <li>click browser_action button</li>
  <li>add div to current tab</li>
  <li>click browser_action button</li>
  <li>remove div</li>
  </ul>