Merge "New hidden API to support the CTS test case that checks the file...

Merge "New hidden API to support the CTS test case that checks the file contents remains unaltered." into udc-dev am: 0fa26314 am: dcc0acb2 am: 7bce424a

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/22839500



Change-Id: I1a4ea504f40f0d7b303cdc39bbab011ad033c535
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>