Merge "[5/n] Pin ActivityStack" into udc-qpr-dev am: fadc3676d6 am: 25e04c2066

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23339404

Change-Id: I49453c1fbdcbaf251fcafcca2e2fcfac03fb54b7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>