Merge "Fix the root task of secondary split screen could be overwritten." into rvc-dev am: 67a056a9 am: 5406617b am: 7fab0918 am: 345c14f7

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/11716093

Change-Id: I20fc6f5b3dd387b557a167e8a3405f3b28c1272c