third_party/WebKit/Source/web/tests/data/root-scroller-iframe.html

<!DOCTYPE html>
<html>
  <head>
    <style>
      ::-webkit-scrollbar {
        width: 0px;
        height: 0px;
      }

      body, html {
        width: 100%;
        height: 100%;
      }

      body {
        margin: 0px;
      }

      iframe {
        width: 100%;
        height: 100%;
        border-style: none;
      }

      #spacer {
        width: 800px;
        height: 800px;
      }
    </style>
  </head>

  <body>
    <iframe src="root-scroller-child.html" id="iframe"></iframe>
    <div id="spacer"></div>
  </body>
</html>