Profile scrolling performance vs. Falkon on ProtonDB Explore

[The-Compiler]

As reported in Laggy/sluggish on some sites : qutebrowser, scrolling performance on sites with heavy background images is rather poor with QtWebEngine. Reported upstream here: [QTBUG-105867] Bad scrolling performance on ProtonDB explore page (background images?) - Qt Bug Tracker.

Example page: ProtonDB | Explore | Most Steam Followers

However, it seems to be worse in qutebrowser than it is in Falkon: https://www.youtube.com/watch?v=Amh7ntEl9QQ

We should probably run that through a profiler and see if there's room for improvement on the qutebrowser side, even if the issue itself is in Qt.