Merge "Downmix : Add libeffect implementation" am: f1a9007f3d am: ecc90a6127

Original change: https://android-review.googlesource.com/c/platform/frameworks/av/+/2353846

Change-Id: I0d63b6570a93b7361d55d47fcc3eb4ebb17d3e1f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>