OneDrive on-demand - files showing full size

When onedrive is used in on-demand mode, the files report their original size, but also a size-on-disk of 0. Please measure the size on disk for onedrive files instead of the reported size.

Start by locating the code that chooses reported size versus size-on-disk for files, then trace how OneDrive on-demand files are represented. Verify the change with an on-demand file whose reported size is nonzero but whose size-on-disk is 0; done means disk usage reflects the on-disk size rather than the original size.

Written by the indexing model from the issue text.