title: Enable CORS in google app engine blobstore downloader
body: <p>I am using "send_blob" to download pdf from google app engine blobstore. How can i enable CORS for this?I have tried adding </p>
  
  <pre><code>self.response.headers.add_header("Access-Control-Allow-Origin", "*")
  </code></pre>
  
  <p>to the function where i call send_blob but it is not working.</p>