[automerger skipped] [RESTRICT AUTOMERGE] Fix UAF in clearkey service's MemoryFileSystem am: 9ba33b35 -s ours

am skip reason: skipped by user edwinwong

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/13711823

Change-Id: I6562f9f8829e7a565bdc54bce723984711c73c4a