How to reproduce:
1. Create a new C# script.
2. Select it in the project view and assign an icon to it in the inspector
3. Create a new Game Object and add the newly created script to it
4. In the Scene View try to select the object by dragging over it

Expected result: The object is selected with no flickering
Actual result: When trying to select the object that has an icon label the selection flickers

Reproduced in: 2018.3.0a6, 2018.2.2f1, 2018.1.9f1, 2017.4.8f1, 2017.2.3p3, 2017.1.5f1