Merge "PiP: Show/hide enter split button based on focused task." into sc-v2-dev am: a656a4e4e4 am: 1fb065c8dc

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16244368

Change-Id: I5700e97a26d5a4a79fb4a065479b3207c716cc69