Allow system to disable behavior of pausing animators for bg apps am: 161732cf

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/18527682



Change-Id: Iab25efc6926ec409ac93769c2d76c88cf8b5bcb6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>