UPDATE 2020/03/04: This issue is no longer relevant, ignore this post.
So recently I needed to attach several files in mails to send, while Google Drive is great for large files I felt that I shouldn’t have to use Google Drive for a few PDFs.
- In Firefox type about:config in the address bar;
- Click the button stating you’ll be careful;
- Search for network.http.spdy.enabled and toggle it to false;
- Try attaching files in GMail.
There a several reasons I prefer Firefox over Google Chrome right now so this fix was needed.