title: Customize Google Charts Gantt tooltip
body: <p>I've tried to customize the tooltip for the Gantt Google Chart and it does not seem to apply</p>
  
  <p>I've added :</p>
  
  <pre><code> data.addColumn({type: 'string', role: 'tooltip'});
  </code></pre>
  
  <p>and options</p>
  
  <pre><code>tooltip: {isHtml: true},
  legend: 'none'
  </code></pre>
  
  <p>But it does not seem to work.
  Below it's a fiddle with the implementation as provided by Google and adapted by me as described above.
  Any idea why it does not work?</p>
  
  <p><a href="https://jsfiddle.net/uped4teh/1/" rel="noreferrer">https://jsfiddle.net/uped4teh/1/</a></p>