Possible leak related to using Nanite meshes for Landscape

A licensee reported that the Bulk data for the nanite mesh generated for Landscape proxies can leak in the editor. It could appear as the normal BulkData “leadk” related to fulling loading an Asset package but in this case, the Bulkdata is owned by a ULandscapeNaniteComponent that is part of one of the external actors. Unloading the level does destroy the Actor and the Component but the BulkData remains.

Please note that this behavior appears to be influenced by the state of the DDC and will only manifest when building the mesh the first time or after modifying the sculpt to need a new mesh

• Create a World-Partition-enabled Level. The default WP level is fine.
• Enable nanite on the Landscape actor.
• Save the new level
• Restart the editor with memory tracing activated
  • -trace=default,memory
• Load the level
• Select a couple LandscapeStreamingProxies
  • In the details panel, hit Build Data in the Nanite section
• Save the result
• Unload the level
• Inspect the Insights trace
  • Generate a growth report with marker A just before the mesh generationg and marker B set after the level was unloaded
  • View by “Alloc Callstack”
  • Search for “FMeshDescriptionBulkData::SaveMeshDescription”.