Merge "DownmixProcess: Add tests to validate the downmix process." into main am: ab269e2fc7 am: 947f4f776c am: 149564ad7e

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2849236

Change-Id: I34f8bdbee50ae15145272544c5546f3ab6aaef15
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>