title: base url inside an iframe is not working correctly
body: <p>I have a web app hosted on <code>http://localhost:3000</code><br>
  and on that web app, I have an iframe with <code>src="http://localhost:8000</code>  </p>
  
  <p>My problem is, relative paths inside that iframe is using <code>http://localhost:3000</code> instead of <code>http://localhost:8000</code> even if I have a base tag inside the iframe</p>
  
  <p>main.html : <code>http://localhost:3000</code>  </p>
  
  <pre><code>&lt;iframe src="http://localhost:8000"&gt;&lt;/iframe&gt;
  </code></pre>
  
  <p>iframe.html : <code>http://localhost:8000</code></p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html lang="en"&gt;
  &lt;head&gt;
    &lt;base href="http://localhost:8000/"&gt;
    &lt;meta charset="UTF-8"&gt;
    &lt;meta name="viewport" content="width=device-width, initial-scale=1.0"&gt;
    &lt;meta http-equiv="X-UA-Compatible" content="ie=edge"&gt;
    &lt;title&gt;Document&lt;/title&gt;
    &lt;link rel="stylesheet" href="/static/assets/css/index.css"&gt;
    &lt;!-- this is using http://localhost:3000 instead of http://localhost:8000 --&gt;
  &lt;/head&gt;
  &lt;body&gt;
  
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/ze6Nr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ze6Nr.png" alt="enter image description here"></a></p>
  
  <p>Am I doing it wrong somewhere?</p>