[automerger skipped] Fix race condition when using mPreserveTopNApps. am:...

[automerger skipped] Fix race condition when using mPreserveTopNApps. am: f81d50e2 am: 09379073 -s ours am: 057c1dda -s ours

am skip reason: Merged-In I8cdf96ed1ddf56261e6ee953fb1078e961a0bc41 with SHA-1 f81d50e2 is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15684473

Change-Id: Id8d241c6568a049b6a5d21e2c19b5c3ab5e74729