When using the GPU profiler and switching between APIs, going back to Directx11 freezes Unity. It looks like a thread lock, because the process on Task manager uses 0% CPU power and the memory usage is constant. I waited for about 5-10 mins an the editor was still frozen.

Repro steps:
1. Open attached project and the Sample Scene
2. Open profiler window and make sure GPU profiler is selected. I also had CPU and Memeory on display
3. Have record on and press play and let the profile run for 1 or 2 secs
4. Switch rendering API to Directx12 and repeat Step 3
5. Switch to Directx11 and repeat Step 3 - it should freeze about now
6. If no freeze, try to focus another window and click back into the profiler window while still in play mode

Reproduced on: 2018.2.0a1->2018.2.0b3 and Trunk

Not reproduced with: 2018.1.0f2 or 2017.4.0f1