b/10968838
The main problem here is that Ui Attachment was always using
a content Uri that was generated using the attachment's account
Id and rowId. This works correctly for attachments in messages
we have received, but it does not work for drafts: Draft attachments
are not stored in the normal place, rather, they are stored in
the cache directory. There is an additional column in the
Attachment table, called cachedFile, which is not replicated in the
Ui attachment. That's okay though, if we have a cachedFile, then
when we are populating a Ui Attachment, we should just use that
for content Uri.
Also, I discoverd that for draft attachments, we were not correctly
setting the account key. That didn't turn out to be the problem,
but I'm fixing it anyway because it will cause problems later on.
Change-Id: I0143ba824f3a5bfcd77f32828931b94d6977626f
f484751e06