Merge "Allow unregistring callbacks in DeviceStateController" into udc-dev am: 7d05f247

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/21890118



Change-Id: Ibdca95c7637b2a0570299824132790760f4635ca
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>