Merge "[1/n] Pin ActivityStack" into udc-qpr-dev am: 82db3963 am: 5b49ff26

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23339396



Change-Id: Ia8ac8fe2dcee01cb56366017e78c165b61c2f9f7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>