title: Alternative to DOMNodeInserted
body: <p>DOMNodeInserted is known to make dynamic pages slow, <a href="https://developer.mozilla.org/en/Extensions/Performance_best_practices_in_extensions" rel="noreferrer">MDN even recommends</a> not using it altogether, but doesn't provide any alternatives.</p>
  
  <p>I'm not interested in the element inserted, I just need to know when some script modifies the DOM. Is there a better alternative to mutation event listeners (maybe getElementsByTagName inside an nsiTimer)?</p>