To reproduce:
1. Open activity monitor
2. Create new project
3. Click RMB and in assets folder(project window) and hold 'option' key
4. Notice how slowly memory usage is growing up
5. If memory usage is not growing, click LMB on the same window and release 'option' key. It should start growing.

Expected result: memory usage will grow up and stop, when RMB table will be loaded.
Actual result: memory usage slowly keeps growing up.

Reproduced on: 5.6.0a3, 5.5.0b10 , 5.5.0b9, 5.4.2f2, 5.3.4.f1, 5.3.1f1;