Serialize resource acqisition to avoid deadlock.

ANR is occuring due to below deadlock.
buildBrowsablePlayerList() -->acquires mBrowsePlayerInfoList
      ->getMediaPlayerInfo(packageName) -->waiting for Avrcp.this
onActiveSessionsChanged() -->acquires  Avrcp.this
      ->isBrowseSupported -->waiting for mBrowsePlayerInfoList

To avoid this ANR serailize resource acqisition.

CRs-Fixed: 2239501
Change-Id: I7f29f5ba1052f10a98c6ed65e1ab7cb900972cd8
1 file changed