User blog comment:Nanamin/Bypassing the DMM Error Area/@comment-1820055-20150805004733/@comment-26171095-20150805011607

Apparently, it binds a listener to chrome.cookies.onChanged and does a check using chrome.cookies.get's callback. The relevant file is here: https://github.com/fcapano/Edit-This-Cookie/blob/master/js/background.js.