http://www.it1352.com/88728.html
external/bluetooth/bluedroid/include/bt_target.h：
* Enable bluetooth av sink. */ #define BTA_AV_SINK_INCLUDED TRUE
Also：
packages/apps/Bluetooth/res/values/config.xml：
<!-- Enable sink support. --> <bool name="profile_supported_a2dp_sink">true</bool>
可能还是没有声音：
Now you can pair your devices and start streaming. Unfortunately you will hear
no sound although you'll receive the packets. The reason is that there is no
audio route for A2DP sink. In the commit message of this patch
https://android-review.googlesource.com/#/c/98161/ you can find a sample
implementation on how to fix this.