@kenchris Thanks for your detailed comments.

Firstly, I have no much strong preference on the attribute naming. A general practice in my mind is the name should be something that can describe the meaning of an attribute very well. Re the unit of capability size, it is assumed to be in bytes, and widely adopted in some other W3C API specs. See [1] for storage quota API, and [2] for the size definition of a file entry.

[1] https://dvcs.w3.org/hg/quota/raw-file/tip/Overview.html#widl-Navigator-storageQuota
[2] http://www.w3.org/TR/file-system-api/#idl-def-Metadata