Fix exposing private messages files through attachments with a content URI.

mentioned in commit f5c73b19

mentioned in commit 5b110f95

mentioned in commit 83d58836

mentioned in commit 471c3e93

mentioned in commit 78c26722

mentioned in commit 6542270a

mentioned in commit a4838ac9

mentioned in commit 749732f4

mentioned in commit 7bf7a451

mentioned in commit 2ffa0171

mentioned in commit 7d9c937d

mentioned in commit fad62338

mentioned in commit 633996e4

mentioned in commit 6daf7c7d

mentioned in commit 9871a34c

mentioned in commit 11d36f6b

mentioned in commit ff1c734a

mentioned in commit 19fa930b

mentioned in commit 35dedd12