Allow system to disable behavior of pausing animators for bg apps am: 161732cf am: 339361ad

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



Change-Id: I4ec75caf30cc4707066aa73b60527c56a9e17912
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>