C2: add support for channel mask am: 65fab753 am: e0743832 am: 85e8a5b0 am: 6eb1b501

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



Change-Id: I12965c79480ff95905b410c8f256d51e1b942610
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>