[automerge] C2Allocator: protetct memory mappings from race condition 2p: 5cbca291 am: a8b5ecd4

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/17806584



Change-Id: I459fcbece901f4580b03435e3a8100ec55c295de
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>