Merge "Cache bluetooth A2DP in AudioService callback thread" am: 163632b1 am: 2727ec6c am: 4d650924

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1545269

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I33588ab3dd09f7b34ed63f876560dcfdc3c01f70