VolumeShaper: Add AudioTrack restore

MediaPlayer VolumeShaper can now be set before start().

Test: CTS and Ducking
Bug: 31015569
Change-Id: Idf63c167e164161b200e2467fbeb9409b3097dbe
diff --git a/media/libmediaplayerservice/MediaPlayerService.h b/media/libmediaplayerservice/MediaPlayerService.h
index dff7322..009fe73 100644
--- a/media/libmediaplayerservice/MediaPlayerService.h
+++ b/media/libmediaplayerservice/MediaPlayerService.h
@@ -165,6 +165,7 @@
         float                   mSendLevel;
         int                     mAuxEffectId;
         audio_output_flags_t    mFlags;
+        sp<VolumeHandler>       mVolumeHandler;
         mutable Mutex           mLock;
 
         // static variables below not protected by mutex