Merge "Merge "Finish supporting floating-IME alpha in split-screen" into rvc-dev am: 9c9434b3 am: 54545eb6 am: 4b6bfc8f" into rvc-qpr-dev-plus-aosp am: f19201a0

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/12130198

Change-Id: I88a5f948d2d4e93f6dafa22b5ff1ca10bd03a52e