An optional list, identical in function to an object's
allowed property,
that specifies the actors
who are allowed to access the media. If the list is undefined
or null, anyone with the URL can access the media. If the list
is empty, only the actor
who posted the media can access it.
data
data:Blob
The binary data of the media to be uploaded,
along with its media type,
formatted as a Blob.
The
actorthatposted the media.