Triaging and repurposing this bug with a more appropiate title now. Elevating priority a bit because this would be a nice cleanup and should be fairly straightforward.

We partially addressed this a while ago by deprecating the unsafe APIs in favor of safe ones which pass around single-ownership handle wrappers.

The old APIs still exist but callers can be migrated. Shared memory wrapping may still be a little trickier as there are so many instances of base::SharedMemory usage around the tree still (as opposed to the newer strongly typed scopers like base::ReadOnlySharedMemoryRegion), and that has fundamentally wonky ownership semantics.