ReturnUntouchedSceneColorForPostProcessing ignores view overrides and breaks splitscreen

When a view extension uses ReturnUntouchedSceneColorForPostProcessing and uses split screen, the final view is incorrect (clipped) because ReturnUntouchedSceneColorForPostProcessing doesn't take into account the dest override.

This can be fixed with by changing FScreenPassTexture::CopyFromSlice in ScreenPass to take into account the override with:

CopyInfo.SourcePosition = FIntVector(ScreenTextureSlice.ViewRect.Min.X, ScreenTextureSlice.ViewRect.Min.Y, 0);

CopyInfo.DestPosition = OverrideOutput.IsValid()

  ? FIntVector(OverrideOutput.ViewRect.Min.X, OverrideOutput.ViewRect.Min.Y, 0)

  : CopyInfo.SourcePosition;

...

return FScreenPassTexture(OutputTexture, OverrideOutput.IsValid() ? OverrideOutput.ViewRect : ScreenTextureSlice.ViewRect);

1. Create a view extension that returns ReturnUntouchedSceneColorForPostProcessing
2. Add a couple local players and enter PIE

Expected

The splitscreen views are correct

Actual

The split screen views are clipped