floss: Fork chromeos metrics from linux

ChromeOS uses the structured metrics that is not built for the Linux
build. Fork the code and fill the implementation for A2dpAudioOverrun.

BUG: 239978865
Tag: #floss
Test: ./build.py
Test: emerge-${BOARD} floss
Test: gd/cert/run
Change-Id: I2ee4bd6fe88ae8477861f538eae021586ad89598