chromium/chrome/browser/resources/intro/default_browser/default_browser.html

<!doctype html>
<html dir="$i18n{textdirection}" lang="$i18n{language}">
  <head>
    <meta charset="utf-8">
    <link rel="stylesheet" href="chrome://resources/css/md_colors.css">
    <link rel="stylesheet" href="chrome://resources/css/text_defaults.css">
    <style>
      body {
        height: 100vh;
        margin: 0;
        width: 100vw;
      }
      @media (prefers-color-scheme: dark) {
        body {
          --md-background-color: rgb(41, 42, 45);
          background-color: var(--md-background-color);
        }
      }
    </style>
  </head>
  <body>
    <default-browser-app></default-browser-app>
    <script type="module" src="/default_browser/app.js"></script>
  </body>
</html>