To reproduce:

1. Get project from case 1203433 (or from here https://drive.google.com/open?id=19GtoEEs8xfjndbX2MjxJl0ThcYrO87DE)
2. Import it.
3. Inspect import window. When

When it starts importing Common uss styleshets, memory usages jumps to 20 GB. Both ADBv2 and ADBv1.
Project is big. Import takes up to 3 hours. Althgough, when importing regular assets, memory is pretty constant at about 3-5 GB. ADB does regular garbage cleanups between different asset imports.

Expected result: Memory should be low. There might be some mistake with allocations or if it's by design to use so much memory, maybe there should be regular garbage colelctions inside the uss importer

Reprodced on: 2020.2.0a1 (2b390ef0ffff)