This is a buggy thing about Chromium. When I's trying to export a .txt file which is in csv format from my website, It displays the content instead of letting me download. I also tried to save the page (CTRL+S) but nothing happened.
After a while, I found a solution, use the developer tool of Chromium:
1. Press F12 to display the developer tool
2. In the Resources tab, click Frames icon, and then Right Click to the file, choose Save As