title: How to change -webkit-scrollbar width when hover on it
body: <p>I want to change the scrollbar width wider, so it looks clear when user hover on it.</p>
  
  <p>So I wrote:</p>
  
  <pre><code>::-webkit-scrollbar {
  width: 7px;
  height: 7px;
  background-color: #ddd;
  }
  ::-webkit-scrollbar:hover {
  width: 10px;
  height: 10px;
  background-color: red;
  }
  </code></pre>
  
  <p>The background color changed to red, but not the width, Is there anyway to solve this? 
  Here is <a href="http://plnkr.co/edit/YPL8pmthXEcnXAUnPyeg?p=preview" rel="noreferrer">plnkr</a> </p>