Add demux to mFrontendTests am: 86aa7010fd am: 6afaf8d190

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2886926

Change-Id: I915317c40513987417d4e0de332e1205c2115d11
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>