title: scrollbar-width:thin not working n Firefox
body: <p>I just implemented the new css scrollbar-color and scrollbar-width in Firefox 67.  The scrollbar-width does not work.  Whether I set it to auto, thin or none it shows the same width.  I want it to be thin, but it's not thin. </p>
  
  <p>Here's how I implemented it.  </p>
  
  <pre><code>:root{
    scrollbar-color:  rgb(75,75,75) black;
    scrollbar-width: thin; 
  </code></pre>
  
  <p>}</p>
  
  <p>It looks good, but it's not thin.  </p>
  
  <p>Thanks for any ideas.  </p>