Merge "UX polish for lock screen preview (1/3)." into tm-qpr-dev am: 9ddeac90

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/21077389



Change-Id: I28bd30d431578ef05cf3a8b8151c0bf571944c7e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>