Merge "Show correct last notification time for grouped notifications" into udc-dev am: f32a80bf

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/21609427



Change-Id: Ia340d0568cba730e51eeca0513dea2e79faf5f00
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>