Add demux to mFrontendTests am: 86aa7010fd am: 6afaf8d190 am: 123934b067 am: 71be20f910 am: d3763ef9fc am: 3be4800e2c

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

Change-Id: Ifcf9b323263e58756518f76cbb164bd087ca35f8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>