Merge "Update nav bar buttons to spec." into tm-qpr-dev am: be17da6e

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/22211739



Change-Id: Id0e8a459ecd14036773d8d1e50e1a3fa7087e143
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>