STAT_VolumetricLightmapBuildData is not counted correctly

STAT_VolumetricLightmapBuildData isn't counted correctly.
It seems that the root cause is Volume.IndirectionTexture.DataSize is set to 0 before STAT_VolumetricLightmapBuildData is decreased.

// PrecomputedVolumetricLightmap.cpp
FPrecomputedVolumetricLightmapData::~FPrecomputedVolumetricLightmapData()
{
	if (!bTransient)
	{
		const SIZE_T VolumeBytes = GetAllocatedBytes(); // <---- GetAllocatedBytes() returns 0
		DEC_DWORD_STAT_BY(STAT_VolumetricLightmapBuildData, VolumeBytes);
	}
}

In the following code, DataSize is cleared.

ENGINE_API void FPrecomputedVolumetricLightmapData::AddToSceneData(FPrecomputedVolumetricLightmapData* SceneData)
{
....
			if (!GIsEditor)
			{
				// Steal the indirection texture. When the sublevels are unloaded the values will be restored.
				IndirectionTexture = SceneData->IndirectionTexture;			
			}

1. Download the attached project on the UDN thread: https://udn.unrealengine.com/s/case/5004z00001k8ioJAAQ/
2. Play a standalone game
3. type "stat MapBuildData" on a console window
4. You can see STAT_VolumetricLightmapBuildData is 0
5. type 1, to load a level
6. type 3, to unload the level loaded before
7. you can see STAT_VolumetricLightmapBuildData is 9MB
8. type 1, to load a level
9. type 3, to unload the level loaded before
10. you can see STAT_VolumetricLightmapBuildData is 18MB...