FileSystem API: Adding file size field to Metadata?

Hi,

While looking at the FileSystem API draft I noticed that we only expose
'modificationTime' in 'Metadata' object.  Since FileEntry itself doesn't
have 'size' field unlike File object maybe it's reasonable to add 'size'
field to Metadata?

http://www.w3.org/TR/file-system-api/#the-metadata-interface

Without adding this we can indirectly get the file size by creating 'File'
object via FileEntry.file() method and accessing File.size, but when an app
wants to display the modificationTime and file size at once (and it sounds
very plausible use case) the app needs to call two different async
methods-- which doesn't sound very nice.  WDYT?

Thanks,
Kinuko