(Web demo) Cursor icon animation lags when cursor not moving

**Describe the bug**

As named, I've opened [web demo](https://www.egui.rs/#demo) and opened "cursor test". When I moved mouse cursor into animated "Progress" and "Wait" fields, animation started lagging. But when I move cursor it's smooth.

Have no idea what it might be or is it reproducible when app is native compiled (i'm not a Rust dev). Anyway, I think it's incorrect behaviour though minor :)

Really sorry for smartphone video, but right after I started screencasting it stopped reproducing. Also not reproducing in Firefox. Don't know whether it might be reproduced while native compiled or not (I'm not a Rust dev).

I have no idea what it might be, maybe it's not the library but chromium or one of gnome components or something else... Anyway, haven't saw those glitches before.

**To Reproduce**
Steps to reproduce the behavior:
1. Open web demo
2. Open cursor test
3. Try to move and not to move cursor on different fields
4. Just like on video

**Screenshots**

Screencast on Chromium (somewhy not reproducing):

[Screencast on Chromium (somewhy not reproducing)](https://github.com/emilk/egui/assets/32620044/2a7772a9-3097-425c-9dde-fb8bab3daf02)

Video on smartphone (runned demo in same browser):

[Video on smartphone (runned demo in same browser)](https://github.com/emilk/egui/assets/32620044/7150fa74-77bb-476d-b477-98385be96535)

**Desktop (please complete the following information):**

- Browser: Chromium (123.0.6312) - fresh installed
- Browser: Brave Browser (v 1.64.122)
- OS: Fedora Linux 39 (Workstation edition)
- Wayland Mutter v 45.5
- Graphics (integrated): AMD Radeon Graphics (AMD Ryzen 5 4600H)
- Graphics (discrete): NVidia GeForce 1650Ti (For laptop)
- Drivers: installed proprietary nvidia drivers, but for now it fails back to nouveau

If i can provide additional info, tell me

Start at the egui.rs web demo and open the “cursor test” to reproduce the lag in Chromium, then compare behavior while the cursor is moving and stationary. Check whether it still occurs on the latest master and in Firefox or a native build; done means establishing a reliable reproduction and narrowing whether the issue is in egui or the browser/runtime.

Written by the indexing model from the issue text.