[automerger skipped] Merge "libutils: use system_background for low prio tasks...

[automerger skipped] Merge "libutils: use system_background for low prio tasks in framework" into sc-qpr1-dev am: ecaf9ef7 -s ours am: b90037af -s ours

am skip reason: Merged-In Iffc47fdaf3ef8fba6eb01a12cf534a0393e3e91c with SHA-1 c39d60d1 is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/core/+/15946148

Change-Id: I23ab4ed61c7f5e5ffef3a6d801a6b0fefb324a54