Merge "New hidden API to support the CTS test case that checks the file contents remains unaltered." into udc-dev am: 0fa26314fe am: a0cbcf65e9 am: d64fd6ad33 am: 0e436a6b12

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

Change-Id: Ie6ea8b74d40ffb471957ccb125f65440fe13635d
Signed-off-by: Automerger Merge Worker <[email protected]>