To reproduce:

1. Open the project, attached by the user (TestProject.zip) and Windows Task Manager
2. Open the "TestScene" scene
3. Enter Play mode
4. Press Space multiple times to spawn particles
5. Observe how memory used by the Editor doesn't increase
6. Select the Particle System object in the Hierarchy and enable Trail module
7. Repeat 4 several times
8. Observe how much memory the Editor uses

Expected: Trail module of the Particle System doesn't leak memory

Reproduced in 5.5.5p1, 5.6.4f1, 2017.1.1f1, 2017.1.2p1, 2017.1.2p1, 2017.2.0f3, 2017.3.0b4