Add audiotrack unit tests am: ba55d5a5 am: 6b2a85a7 am: 4695cf00

Original change: https://android-review.googlesource.com/c/platform/frameworks/av/+/2189999



Change-Id: I1e40de4c40cf01a2844c184d4d28eac1b6311ded
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>