PDF import page periodically reloads entirely until the file is ready

Steps to reproduce:

1) Go to https://musescore.com/import

2) Add a given pdf file

3) As the server is loading, the page is repeatedly reloaded entirely.

The page reloads to poll the result as opposed to polling the server in the background and only reloading the element when ready. This is inefficient and generally a worse experience to the user.