Merge "Clear DreamOverlayCallback reference on destroy." into udc-qpr-dev am: 651440d1

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/24122170



Change-Id: I8d66bf972f2b28741698eae6758938505ffd2202
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>