Slow Requests Using HTTP2

I recently switched to using HTTP2 in my application by setting the QNetworkRequest HTTP2AllowedAttribute to True for all my requests. I immediately noticed some of my downloads were going way slower than normal.

I have been using 5.10 Alpha for the OpenSSL 1.1.x support and ran the following tests:

My home connection DL Speed: 175 Mbit/s
Test URLs for both HTTP/HTTPs (Note from tipochep: url with 'http' scheme and HTTP/2 == true shows 175 Mbit/s because the server ignores protocol upgrade and it's essentially HTTP/1.1)

http://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/jquery-speedtest/100MB.txt

https://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/jquery-speedtest/100MB.txt

Results:

http URL w/ HTTP2AllowedAttribute = False: 175 Mbit/s
http URL w/ HTTP2AllowedAttribute = True : 175 Mbit/s (ProtocolFailure in 5.9, but fixed in 5.10)
https URL w/ HTTP2AllowedAttribute = False: 175 Mbit/s
https URL w/ HTTP2AllowedAttribute = True: ~7-8 Mbit/s

So the issue happens when using TLS/SSL AND the HTTP2AllowedAttribute set to True