Add demux to mFrontendTests am: 86aa7010fd am: 6afaf8d190 am: 123934b067 am: 71be20f910 am: aa02c517d3

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

Change-Id: I6fa0e47c83056f93b7a770bd8bed8f21a3e30d6d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>