AudioTrack: add support for compressed audio

Add support for compressed audio playback by use
of an AudioTrack attached to a direct output thread.

Bug: 9428304.

Change-Id: I4a61be9cf0e31003ca85935d6e0ee38ca8192e03
diff --git a/include/media/IAudioFlinger.h b/include/media/IAudioFlinger.h
index c742810..fc8be20 100644
--- a/include/media/IAudioFlinger.h
+++ b/include/media/IAudioFlinger.h
@@ -50,6 +50,7 @@
         TRACK_TIMED   = 1,  // client requests a TimedAudioTrack
         TRACK_FAST    = 2,  // client requests a fast AudioTrack or AudioRecord
         TRACK_OFFLOAD = 4,  // client requests offload to hw codec
+        TRACK_DIRECT = 8,   // client requests a direct output
     };
     typedef uint32_t track_flags_t;