/system/lib/hw/audio.a2dp.default.so, bluetooth.default.so <br>
/system/vendor/lib/libbt-vendor.so <br>
To build bluedroid library for your device, please do like this:
https://github.com/shuangMoz/device-mako/commit/58a9889b70f1c21b52386af8800d0e525cd4947c
For bcm chipset, source code in device/common/libbt