AudioFlinger: Extract inner TrackHandle and RecordHandle classes

Test: atest audiorecord_tests audiotrack_tests audiorouting_tests trackplayerbase_tests audiosystem_tests
Test: atest AudioTrackTest AudioRecordTest
Test: YouTube, Camera
Bug: 288339104
Bug: 288468076
Merged-In: Ifc76e2aa4b6df801595d3ecc6b173dbc81cb9e3f
Change-Id: Ifc76e2aa4b6df801595d3ecc6b173dbc81cb9e3f
(cherry picked from commit a5a7fc9604696f724ab0515f6937e691375b119a)
diff --git a/services/audioflinger/Threads.h b/services/audioflinger/Threads.h
index ed75fc0..57b82b4 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -847,8 +847,6 @@
                 void dumpEffectChains_l(int fd, const Vector<String16>& args);
 };
 
-private:
-
 class VolumeInterface {
  public:
 
@@ -2375,3 +2373,5 @@
     float mVolumeLeft = 0.f;
     float mVolumeRight = 0.f;
 };
+
+private: