[automerger skipped] Refactor HintManagerService locking to fix race am: 3f40610ee8 -s ours

am skip reason: Merged-In I36670f144bc638143ebbe785885ace8aa957f40c with SHA-1 c036518355 is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/27101360

Change-Id: Ifd6b897da0ae8e03da1e7d89fbb02fb7f77d3fc8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>