Merge "Optimize attaching / detaching audio mixes." into udc-dev am: 12504654

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/22607657



Change-Id: I4b37f79dbf9e213ec1447a7f2b33c52a16330226
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>