Steps to repro:

1. Open Unity;
2. Open attached project and 'test' scene;
3. Select Terrain gameobject in the Hierarchy view;
4. Choose any unique brush preset (for example, a star);
5. Switch to the 'Paint trees' tab;

6. Observe that brush is rendered like a big circle with rough edges;
7. Switch back to 'Paint Height' tab;
8. Observe brush rendering in Scene view.

Actual result:
After switching back from 'Paint Trees' tab brush is rendered like a circle with rough edges, yet other brush (star) is selected. See attached actual.png screenshot and gif video.

Expected result:
After switching back from 'Paint Trees' tab previously chosen tab should be rendered on terrain's brush in Scene view. See attached expected.png screenshot.

Notes:
- Reproducible in 5.5.0b7, 5.4.1f1, 5.3.5p2, 5.2.2p4;
- Reproducible on both Windows 10 and OSX 10.12;
- Reproducible only when switching back from 'Paint tree' tab;
- Brush still works correctly when painting on terrain; the issue is only in scene view rendering.