Steps to reproduce:
1. Build and run attached project's scene "MouseDeltaTestScreen" to WebGL.
2. Set FPS to 15 (Input field in upper left corner).
3. Press "LockCursor" button.
4. Try controlling cube - there's a delay and not the best precision.
5. Build and run to standalone (tested on windows).
6. Repeat steps 2-3.
7. Cube moves more fluently.

Reproduced on Windows 10 with 5.4.0b9, 5.3.3f1, 5.3.1f1
Does not reproduce on 5.2.4f1