AudioFlinger: Remove naked track pointers

Test: Play Music offloaded and kill audioserver
Change-Id: I3114a67f248e067e0b5334d76e4b5e6c39858040
diff --git a/services/audioflinger/Threads.h b/services/audioflinger/Threads.h
index 1fd2adc..862dc51 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -1077,7 +1077,7 @@
     DirectOutputThread(const sp<AudioFlinger>& audioFlinger, AudioStreamOut* output,
                         audio_io_handle_t id, uint32_t device, ThreadBase::type_t type,
                         bool systemReady);
-    void processVolume_l(Track *track, bool lastTrack);
+    void processVolume_l(sp<Track> track, bool lastTrack);
 
     // prepareTracks_l() tells threadLoop_mix() the name of the single active track
     sp<Track>               mActiveTrack;