title: Google drive resumable upload and CORS
body: <p>I'm using the google drive resumable upload API and am seeing a lack of CORS headers in some cases. The pre-flight to OPTIONS always returns 200 but when making the actual requests, the headers are missing in some cases, which means I am not able to read the responses.</p>
  
  <p>Not seeing CORS headers when:
   - uploading the final chunk
   - creating a resumable session
   - querying for session status</p>
  
  <p>Seeing CORS headers when:
   - uploading a non-final chunk (308 status response)</p>