[automerger skipped] [RESTRICT AUTOMERGE] Fix UAF in clearkey service's...

[automerger skipped] [RESTRICT AUTOMERGE] Fix UAF in clearkey service's MemoryFileSystem am: 9ba33b35 -s ours am: 0a2abba4 -s ours am: a4e3bea9 am: 0245e885 am: ea7e6b49 -s ours am: e7732579

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

Change-Id: I53ada727ad1932f87d2fa69c11fc36f61c1d349d