NavMeshDisplay is not shown if Navigation window located in the editor that its always visible.

Use any project to reproduce (empty is also possible)
- locate Navigation window in a separate place in the editor (it shouldn't hide when you focuse on another windows). Notice that "NavMesh Display" window is shown.
- enter end exit play mode.
- notice that "NavMesh Display" window is not shown anymore. Focusing on Navigation window doesn't help.