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: I5922808fa09ea3a0131d04a2f6fc89ac87c076a2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>