Merge "Add hover and pressed states to notification expand button" into udc-qpr-dev am: 19abdf19

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23790862



Change-Id: I7fccf50a68aa38999972f0fab34abeaa1772e0bf
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>