When the blackboard window is set to "Fit" and Shader graph window is resized, The blackboard window flickers refer to the attached video.

Steps to repro:
1. Create a new project
2. Windows > Package Manager > Shader Graph > Install
3. Project window > Create > Shader > PBR Graph
4. Blackboard > add properties (Vector 1, Color)
5. Blackboard window set fit to Shader Graph window
6. Resized the Shader Graph window

Actual Result:
"Blackboard" window flickers on resizing the "Shader Graph" window

Expected Result:
Blackboard window doesn't flicker and automatically get adjusted with Shader Graph window

Note: Blackboard window not flickers if it is not set fit to Shader Graph window

Occurring on:
2020.2.0a5, 2020.1.0b4, 2019.3.8f1, 2019.2.13f1, 2019.1.11f1, 2018.4.14f1, 2018.3.0f2, 2018.1.0f2

Package found version:
8.0.1, 7.3.1, 7.1.8, 7.0.0, 6.9.2, 1.1.9 - preview

Environment:
Occurs only on Windows10