chromium/ash/webui/help_app_ui/resources/index_dark_light.html

<!-- Copyright 2019 The Chromium Authors
     Use of this source code is governed by a BSD-style license that can be
     found in the LICENSE file. -->
<!DOCTYPE html>
<html dir="$i18n{textdirection}" lang="$i18n{language}">
<head>
  <meta charset="utf-8">
  <title>$i18n{appTitle}</title>
  <style>
    body {
      height: 100vh;
      margin: 0;
      overflow: hidden;
    }

    /*
     * Any changes to this file except for these media queries should also be
     * copied to index.html.
     */
    @media (prefers-color-scheme: dark) {
      body { background-color: #202124 }
    }

    @media (prefers-color-scheme: light) {
      body { background-color: white }
    }

    /*
    * This is the <iframe> style set for sandboxed guests that use
    * guest_view_iframe_container.js.
    */
    iframe {
      border: 0;
      display: block;
      height: 100%;
      width: 100%;
    }
  </style>
</head>
<body>
  <script src="/browser_proxy.js" type="module"></script>
</body>
</html>