Log track name on obtain/releaseBuffer warnings

This should help diagnose problems by allowing us to correlate
the logs with the dumpsys media.audio_flinger output.

Change-Id: I8c7c592b4f87d13b0f29c66ce7a2f301a0f063c9
diff --git a/include/private/media/AudioTrackShared.h b/include/private/media/AudioTrackShared.h
index 469f5ff..5b133f3 100644
--- a/include/private/media/AudioTrackShared.h
+++ b/include/private/media/AudioTrackShared.h
@@ -97,9 +97,7 @@
 
                 // read-only for client, server writes once at initialization and is then read-only
                 uint8_t     frameSize;       // would normally be size_t, but 8 bits is plenty
-
-                // never used
-                uint8_t     pad1;
+                uint8_t     mName;           // normal tracks: track name, fast tracks: track index
 
                 // used by client only
                 uint16_t    bufferTimeoutMs; // Maximum cumulated timeout before restarting audioflinger