Fix exposing private messages files through attachments with a content URI. am: 0d5452146c am: f5c73b1923 am: 83d5883687 am: fad62338f9 am: 633996e4bb

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Messaging/+/23089831

Change-Id: I62d531ec009270bb3b3eae8f5cd02e5462441e9b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>