1. Open attached project and open HDRtest scene
2. Select Main camera and inspect Occlusion Culling, Allow HDR and Allow MSAA settings
3. Toggle HDR on and off repeatedly
4. Observe Camera preview and Game view
5. At times there should be visible random leftovers from rendering, ghost cubes, purple/pink pixels in the background (which is supposed to be black)

Expected outcome: Depth only clear flag doesn't clear the buffer, so the cube smears across the Game view when moved.
Actual outcome: HDR enabled starts clearing the buffer, but only when there's no other camera clearing the background. At times it also just shows up with some artifacts

Reproduced on 5.6.0f3 , 5.5.3f1, 5.4.0f3
Does not reproduce in 2017.1.0b1

Note: in 5.5.3f1 the camera seems to switch between two different buffers without clearing them. This is when using Deferred rendering.
5.4.0f3 functions similarly to 5.5.3f1