Cache MMAP client silenced state. am: 5ee3824389

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/19382430

Change-Id: I19e6e5afbfdd0eb8769764929ef08b7a0c961f56
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>