title: Chrome headless does not load iframe content (json-ld)
body: <p>I want to render this page <a href="https://ofertypracy.monsterpolska.pl/system-integration-java-engineer-krak%C3%B3w-mal-poland-grafton-recruitment/11/200672360" rel="nofollow noreferrer">CLICK</a> and get html as string. So I use this code:</p>
  
  <pre><code>public class ChromeRender implements RenderService {
      private final static Logger LOGGER = Logger.getLogger(ChromeRender.class.getName());
  
      private final WebDriver driver;
  
      public ChromeRender() {
          ChromeOptions options = new ChromeOptions();
          options.addArguments( "--headless --window-size=1920,1200","--ignore-certificate-errors");
          options.addArguments("--user-agent=New User Agent");
          options.addArguments("--disable-features=top-document-isolation,site-per-process");
          this.driver = new ChromeDriver(options);
      }
  
      @Override
      public String renderPage(String url) {
          var start = System.currentTimeMillis();
          driver.get(url);
          LOGGER.info("Page downloaded in "+ (System.currentTimeMillis()-start) + " ms");
          System.out.println(driver.getPageSource());
          return driver.getPageSource();
      }
  }
  </code></pre>
  
  <p>The problem is that, invoked method getPageSource() returns html but without iframe content rendered. In browser, content is rendering just fine - there is nice html tree with content I want. But result from method .getPageSource() returns html without iframe properly rendered. Whats the problem here? Is this method supposed to return html as string that is equal to what I see in browser? </p>