C2: add support for channel mask am: 65fab753 am: e0743832

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



Change-Id: I3dd25b5a55f739e9787725d784c6b55c48c7e997
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>