How to reproduce:
1. Create a new project in your preferred workspace
2. Open it and connect it to Perforce
3. Create a 100 new materials (Just so you would have something to scroll through)
4. Select all of the materials and try to Revert them
5. In the Revert window scroll using the scroll bar (Observe that it's fast)
6. Try to scroll using the mouse wheel (Observe that it's very slow)

Expected result: scrolling with the mouse wheel is fast
Actual result: scrolling with the mouse wheel feels laggy and takes around 1-3 secs to update the list

Reproduced in: 2020.1.0a9, 2019.3.0b7, 2019.2.10f1, 2018.4.11f1, 2017.4.33f1

Note: Reproduces both on Mac and Windows