Steps to reproduce:
1. Create a new project
2. Create material in Project window
3. Create ParticleSystem in the scene, and select it to simulate (easiest to see effect with Particle system)
4. In Project window pick up material and hold it picked up without moving a mouse

Expected result: Editor starts lagging, can see that from particle simulation slowing down, also increased activity is visible in Profiler
Actual result: No major impact on the performance

Reproducible: 2017.4.18f1, 2018.3.1f1, 2019.1.0a13, 2019.2.0a6

Not reproducible on Mac (2017.4.18f1 - no performance change, 2018.3.1f1 and 2019.1.0a13 - Editor stops updating when object is picked)