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

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



Change-Id: I020c589ceba7d76cff80890b71bc560583f21bd3
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>