Merge "Add MOUNT_FLAG_VISIBLE to visible stub volumes" am: d8e3e07264 am: eba787f7a5

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1536320

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I21d5560f0d061cae9c8959cb658a75fd14e7ed76