How to reproduce:
1. Create a new LWRP/HDRP project
2. Create a new Shader/Find an existing Shader
3. Open the Profiler window
4. Select the Memory module and profile Editor
5. Note the Material count
6. Select the Shader in the Project window while having Inspector window open
7. See the Material count again

Expected result: Material count does not increase
Actual result: Material count increases

Reproducible with Unity versions: 2018.3.0b7, 2018.4.5f1, 2019.1.0a4, 2019.1.13f1, 2019.2.0f1, 2019.3.0a11
Not reproducible with Unity versions: 2018.3.0b6, 2019.1.0a1, 2019.1.0a3
Could not test with Unity versions: 2017.4.31f1(LWRP/HDRP packages not available)

Reproducible with LWRP package versions: 2.0.6, 7.0.0
Could not test with LWRP package versions: 2.0.5 (version incompatibility errors)

Notes:
Also reproduced with HDRP; does not reproduce with the default Render Pipeline
Does not reproduce when Inspector window is inactive/closed