Steps to repro:

1. Open Unity;
2. Create new project and scene;
3. Add Terrain gameobject (GameObject -> 3D Object -> Terrain);
4. Go to 'Paint Height' tab of Terrain component;
5. Resize Inspector to the minimum width size;
6. Observe Height scalebar.

Actual result:
Height scalebar disappears when resizing Inspector in 'Paint Height' tab (see attached gif video and actual.png). Inconsistent with other scalebars within Terrain component.

Expected result:
Height scalebar disappears should not disappear when resizing Inspector in 'Paint Height' tab.

Notes:
- Reproducible in: 5.4.0b8, 5.4.0b7, 5.3.3p2, 5.3.2f1, 5.2.0f3;
- Reproducible on both OSX 10.11.3 and Windows 10.