Merge "Call DecorView.drawableChanged() in PhoneWindow.setBackgroungDrawable" into rvc-qpr-dev am: 7ce178e6cb am: bf26b5a9f4

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

Change-Id: I6305948aea70c8283c2670caad61a1a6699b174c