Merge "Add support for flag change listeners library." into sc-v2-dev am: c61d506a am: 6a9f7f79

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16182385

Change-Id: Ic4e7ec1b6b80e6690d06c50e66751ee4162d48ae