Merge "Apply root task for launch activity animation." into udc-dev am: 181bcdba

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23109637



Change-Id: I6174026c52ccbadb000e2f4719d0cd8c7f642dc7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>