Merge "[7/n] Pin ActivityStack" into udc-qpr-dev am: 0926aa9033

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/24368154

Change-Id: I350744f6eb798464c6ea7ee5654fce96fa57cca7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>