chromium/chrome/test/data/android/previewtab/preview_tab.html

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, user-scalable=no">
  <title>Preview Tab Preview</title>
</head>
<body style="background-color:powderblue;">
  <h1>Preview Tab</h1>
  <p>This is a test Preview Tab. It has content the that user wants to look at quickly before returning to the Base Page that they started with, and is providing some context by still remaining partionally in view.</p>
  <p>Here's a link to another page used to test trying to bring up a Preview Tab within a Preview Tab: another
  <a href="another_page.html" id="anotherPage">page</a>.
     Taking the link should be possible, using navigation within the Preview Tab.</p>
</body>
</html>