Implement GetRootOfTrust am: 18cf62712c

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/core/+/18868385

Change-Id: I856bef5cf27ca209838202ca3668abbaf0f20e56
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>