title: Is a Http2 Cross-origin push request possible?
body: <p>Say I have a server that serves an HTML file at the url <code>https://example.com/</code> and this refers to a css file at the url <code>https://test.com/mystyles.css</code>.  Is it possible to push the <code>mystyles.css</code> file alongside the html content as part of an HTTP2 connection, so that a browser will use this css content?</p>
  
  <p>I have tried to create such a request using a self-signed certificate on my localhost (and I have pre-created a security exception for both hosts in my browser) by sending the html file when a request arrives at <code>http://localhost/</code>, and pushing the css with a differing hostname/port in the <code>:authority</code> or <code>Host</code> header. However, on a full-page refresh, the CSS file is fetched in a separate request from the server, rather than using the pushed css file.</p>
  
  <p>See <a href="https://gist.github.com/benwhite-deltas/f667d8db5a1ad837eabe" rel="noreferrer">this gist</a> for a file that I have been using to test this. If I visit <code>http://localhost:8080/</code> then the text is red, but if I visit <code>http://test:8080/</code> it is green, implying that the pushed content is used if the origin is the same.</p>
  
  <p>Is there a combination of headers that needs to be used for this to work? Possibly invoking CORS?</p>