"ProBuilder Window" tooltip appears truncated.

Steps to reproduce:
1. Create a new project.
2. Go to Window > Package Manager > ProBuilder package (Version 4.0.4) > Install.
3. Go to Tools > ProBuilder > ProBuilder Window.
4. Right-click anywhere in blank area > Use Icon Mode.
5. Hover mouse over cogwheel of Lightmap UV's icon.

Note: Screenshot is attached for the reference.

Actual result:
Toolbar tooltip appears truncated.

Expected Result:
Toolbar tooltips rendering properly.

Reproducible in: 2019.2.0a13, 2019.1.0f2, 2019.1.0b2

Not reproducible in: 2019.1.0b1, 2018.3.0f2

Environment: Windows only.