title: Unique id for each Firefox & Chrome extension installation
body: <p>Is there a way to generate something like a "computer id" that will be different on each computer on from a firefor and chrome extension to use for tracking purposes?</p>
  
  <p>I mean, I want each extension installation to have a unique id that will be always the same on that computer, but different on each computer.</p>
  
  <p><em>The id doesn't need to be the same on both chrome and firefox extension</em></p>