Merge "Add documentation to VibratorManager on foreground/background behavior" into sc-dev am: 03b86cd1 am: 887404ac am: a88824d4

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/14734462

Change-Id: I884535b8008f866067629f6aeac8f6d8a61d7881