C2: add support for channel mask am: 65fab753 am: 3dbbc760 am: 917ebd61 am: 91b18d8a

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



Change-Id: Ie56019e897f67e018e5fedc222e16d94aad086e9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>