title: Chrome remote debugging protocol, getAllStyleSheets() method not found
body: <p>I am trying to access all stylesheets from a Chrome extension using the Remote debugging protocol. According to <a href="https://chromedevtools.github.io/debugger-protocol-viewer/CSS/" rel="nofollow">https://chromedevtools.github.io/debugger-protocol-viewer/CSS/</a> there should be a method for this:</p>
  
  <blockquote>
    <p>A client can also discover all the existing stylesheets with the
    getAllStyleSheets() method</p>
  </blockquote>
  
  <p>However I was unable to execute this. Is this implemented? Is there another way of accessing the CSSOM from a background script</p>