Implement GetRootOfTrust am: 18cf62712c

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

Change-Id: Icf12c572faf7b17a0207218a2859d013c96d3346
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>