Merge "Call DecorView.drawableChanged() in PhoneWindow.setBackgroungDrawable" into rvc-qpr-dev am: 7ce178e6cb

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/12685846

Change-Id: I438591f2faa40c9ab80a8d774b48de7e7a1f9e1b