DO NOT MERGE: Fix ActivityManager#killBackgroundProcesses permissions am: 140fce8619

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/25119905

Change-Id: I113b06a3cddd22b160677afcaddb162a605e87ee
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>