Merge "Update letterbox restart dialog style to match other Android U dialogs" into udc-dev am: 565b8127 am: 3a71e091

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23561836



Change-Id: I9a1323116c6844afdfc3a926664985e0fe791018
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>