Steps to reproduce:
1. Open QA attached project
2. Select Main camera
3. Have 2 displays, one with a larger and the other with a smaller resolution
4. Bring the inspector to the smaller resolution monitor
5. Click on the list for the KeyCode variable
6. Observe that the list can't be scrolled, because the triangle is below the screenspace

Expected: Based on the resolution, the list should be shortened and scrolled appropriately
Actual: The scroll button for the list is offscreen and inaccessible

Reproduced on 5.5.4p1, 5.6.2p4, 2017.1.0f3, 2017.2.0b3

Note: If you lower the resolution with a window further away towards the side, there might come a scenario where there is a window behind screenspace and it's completely unreachable.