C2: add support for channel mask am: 65fab753 am: 3dbbc760

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/17478658



Change-Id: I2d6d0cbf9ac9be83d5c55e847b8ed60ec2d67f9c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>