title: Generate an HTML page, and open in a new window, from a Vaadin 8 app
body: <p>From my Vaadin 8 web app, I want the user to be able to open a report in another window, by clicking a button. The contents are to be generated by the Vaadin app using plain HTML5 rather than using Vaadin widgets.</p>
  
  <p>The Vaadin 8 manual has a page <a href="https://vaadin.com/docs/v8/framework/advanced/advanced-windows.html" rel="noreferrer"><em>Handling Browser Windows</em></a>. Its shows the use of a <code>BrowserWindowOpener</code> object to open a new window. But that window contains a Vaadin <code>UI</code> subclass, whereas I want to generate my own HTML content.</p>
  
  <p>Bonus points for passing information such as a database identifier value.</p>